diff --git a/src/savedata.c b/src/savedata.c
index c85f06f..4a02856 100644
--- a/src/savedata.c
+++ b/src/savedata.c
@@ -43,7 +43,12 @@ typedef int emscripten_align1_int;
 #include "selection.h"
 #include "message.h"
 
-#define SAVE_DATAID "System3.5 SavaData(c)ALICE-SOFT"
+const char *save_signature[] = {
+	[SAVEFMT_XSYS35] = "System3.5 SavaData(c)ALICE-SOFT",
+	[SAVEFMT_SYS36]  = "System3.5 SaveData(c)ALICE-SOFT",
+	[SAVEFMT_SYS38]  = "System3.8 SaveData(c)ALICE-SOFT",
+};
+
 #define SAVE_DATAVERSION 0x350200
 
 typedef struct {
@@ -108,15 +113,17 @@ typedef struct {
 	emscripten_align1_int rsv2;
 } Ald_sysVarHdr;
 
-static int saveStackInfo(FILE *fp);
-static void  loadStackInfo(char *buf);
-static void* saveStrVar(Ald_strVarHdr *head);
-static void  loadStrVar(char *buf);
+static int saveStackInfo(enum save_format format, FILE *fp);
+static void loadStackInfo(enum save_format format, char *buf);
+static void* saveStrVar(enum save_format format, Ald_strVarHdr *head);
+static void loadStrVar(enum save_format format, char *buf);
 static void* saveSysVar(Ald_sysVarHdr *head, int page);
 static int   loadSysVar(char *buf);
 static void* loadGameData(int no, int *status, int *size);
 static int   saveGameData(int no, char *buf, int size);
 
+static enum save_format save_format = SAVEFMT_XSYS35;
+
 #ifdef __EMSCRIPTEN__
 EM_JS(void, scheduleSync, (), {
 	xsystem35.shell.syncfs();
@@ -125,6 +132,22 @@ EM_JS(void, scheduleSync, (), {
 #define scheduleSync()
 #endif
 
+int save_setFormat(const char *format_name) {
+	if (!strcmp(format_name, "xsystem35"))
+		save_format = SAVEFMT_XSYS35;
+	else if (!strcmp(format_name, "system36"))
+		save_format = SAVEFMT_SYS36;
+	else if (!strcmp(format_name, "system38"))
+		save_format = SAVEFMT_SYS38;
+	else if (!strcmp(format_name, "system39"))
+		save_format = SAVEFMT_SYS38;
+	else {
+		WARNING("unknown save format %s", format_name);
+		return NG;
+	}
+	return OK;
+}
+
 /* savefile を参照 */
 const char *save_get_file(int index) {
 	return nact->files.save_fname[index];
@@ -380,8 +403,18 @@ int save_loadAll(int no) {
 		WARNING("endian mismatch");
 		goto errexit;
 	}
-	if (strcmp(SAVE_DATAID, save_base->ID) != 0)
+	enum save_format format = (enum save_format)-1;
+	for (int i = 0; i < sizeof(save_signature) / sizeof(save_signature[0]); i++) {
+		if (!strcmp(save_signature[i], save_base->ID)) {
+			format = i;
+			break;
+		}
+	}
+	if (format < 0) {
+		WARNING("unrecognized save format");
 		goto errexit;
+	}
+
 	nact->sel.MsgFontSize        = save_base->selMsgSize;
 	nact->sel.MsgFontColor       = save_base->selMsgColor;
 	nact->sel.WinBackgroundColor = save_base->selBackColor;
@@ -390,10 +423,12 @@ int save_loadAll(int no) {
 	nact->msg.MsgFontColor       = save_base->msgMsgColor;
 	nact->msg.WinBackgroundColor = save_base->msgBackColor;
 	nact->msg.WinFrameColor      = save_base->msgFrameColor;
-	sl_jmpFar2(save_base->scoPage, save_base->scoIndex);
+	sl_jmpFar2(save_base->scoPage - (format == SAVEFMT_XSYS35 ? 0 : 1), save_base->scoIndex);
 
 	for (i = 0; i < SELWINMAX; i++) {
-		int j = (i + 1) % SELWINMAX;  // For savedata compatibility
+		int j = format == SAVEFMT_XSYS35
+			? (i + 1) % SELWINMAX  // For savedata compatibility
+			: i;
 		nact->sel.wininfo[j].x      = save_base->selWinInfo[i].x;
 		nact->sel.wininfo[j].y      = save_base->selWinInfo[i].y;
 		nact->sel.wininfo[j].width  = save_base->selWinInfo[i].width;
@@ -401,7 +436,9 @@ int save_loadAll(int no) {
 		// nact->sel.wininfo[i].save   = TRUE;
 	}
 	for (i = 0; i < MSGWINMAX; i++) {
-		int j = (i + 1) % MSGWINMAX;  // For savedata compatibility
+		int j = format == SAVEFMT_XSYS35
+			? (i + 1) % MSGWINMAX  // For savedata compatibility
+			: i;
 		nact->msg.wininfo[j].x      = save_base->msgWinInfo[i].x;
 		nact->msg.wininfo[j].y      = save_base->msgWinInfo[i].y;
 		nact->msg.wininfo[j].width  = save_base->msgWinInfo[i].width;
@@ -410,9 +447,9 @@ int save_loadAll(int no) {
 		// nact->msg.wininfo[i].save   = FALSE;
 	}
 	/* スタックのロード */
-	loadStackInfo(saveTop + save_base->stackinfo);
+	loadStackInfo(format, saveTop + save_base->stackinfo);
 	/* 文字列変数のロード */
-	loadStrVar(saveTop + save_base->varStr);
+	loadStrVar(format, saveTop + save_base->varStr);
 	/* 数値・配列変数のロード */
 	for (i = 0; i < 256; i++) {
 		if (save_base->varSys[i] != 0) {
@@ -430,6 +467,7 @@ int save_loadAll(int no) {
 
 /* データのセーブ */
 int save_saveAll(int no) {
+	enum save_format format = save_format;
 	Ald_baseHdr   *save_base = calloc(1, sizeof(Ald_baseHdr));
 	Ald_strVarHdr save_strHdr;
 	Ald_sysVarHdr save_sysHdr;
@@ -454,7 +492,7 @@ int save_saveAll(int no) {
 	memset(&save_sysHdr, 0, sizeof(Ald_sysVarHdr));
 	
 	/* 各種データのセーブ */
-	strncpy(save_base->ID, SAVE_DATAID, 32);
+	strncpy(save_base->ID, save_signature[format], 32);
 	save_base->version       = SAVE_DATAVERSION;
 	save_base->selMsgSize    = (uint8_t)nact->sel.MsgFontSize;
 	save_base->selMsgColor   = (uint8_t)nact->sel.MsgFontColor;
@@ -464,11 +502,13 @@ int save_saveAll(int no) {
 	save_base->msgMsgColor   = (uint8_t)nact->msg.MsgFontColor;
 	save_base->msgBackColor  = (uint8_t)nact->msg.WinBackgroundColor;
 	save_base->msgFrameColor = (uint8_t)nact->msg.WinFrameColor;
-	save_base->scoPage       = sl_getPage();
+	save_base->scoPage       = sl_getPage() + (format == SAVEFMT_XSYS35 ? 0 : 1);
 	save_base->scoIndex      = sl_getIndex();
 	
 	for (i = 0; i < SELWINMAX; i++) {
-		int j = (i + 1) % SELWINMAX;  // For savedata compatibility
+		int j = format == SAVEFMT_XSYS35
+			? (i + 1) % SELWINMAX  // For savedata compatibility
+			: i;
 		save_base->selWinInfo[i].x      = (uint16_t)nact->sel.wininfo[j].x;
 		save_base->selWinInfo[i].y      = (uint16_t)nact->sel.wininfo[j].y;
 		save_base->selWinInfo[i].width  = (uint16_t)nact->sel.wininfo[j].width;
@@ -476,7 +516,9 @@ int save_saveAll(int no) {
 	}
 	
 	for (i = 0; i < MSGWINMAX; i++) {
-		int j = (i + 1) % MSGWINMAX;  // For savedata compatibility
+		int j = format == SAVEFMT_XSYS35
+			? (i + 1) % MSGWINMAX  // For savedata compatibility
+			: i;
 		save_base->msgWinInfo[i].x      = (uint16_t)nact->msg.wininfo[j].x;
 		save_base->msgWinInfo[i].y      = (uint16_t)nact->msg.wininfo[j].y;
 		save_base->msgWinInfo[i].width  = (uint16_t)nact->msg.wininfo[j].width;
@@ -487,12 +529,12 @@ int save_saveAll(int no) {
 	
 	/* スタック情報 */
 	save_base->stackinfo = totalsize;
-	totalsize += saveStackInfo(fp);
+	totalsize += saveStackInfo(format, fp);
 	if (ferror(fp))
 		goto errexit;
 	
 	/* 文字列変数 */
-	if (NULL == (sd_varStr = saveStrVar(&save_strHdr)))
+	if (NULL == (sd_varStr = saveStrVar(format, &save_strHdr)))
 		goto errexit;
 	
 	if (1 != fwrite(&save_strHdr, sizeof(Ald_strVarHdr), 1, fp))
@@ -526,6 +568,49 @@ int save_saveAll(int no) {
 	if (1 != fwrite(save_base, sizeof(Ald_baseHdr), 1, fp))
 		goto errexit;
 	
+	if (format != SAVEFMT_XSYS35) {
+		// Padding(?)
+		fseek(fp, 0L, SEEK_END);
+		for (int i = 0; i < 256; i++)
+			fputc(0xff, fp);
+		// Write a mark to indicate that this file was created by xsystem35.
+		fputs("XS35", fp);
+	}
+	if (format == SAVEFMT_SYS38) {
+		// Stack info
+		struct stack_info sinfo;
+		sl_getStackInfo(&sinfo);
+		int size = sinfo.page_calls * 2 + sinfo.label_calls;
+		int *buf = calloc(size, sizeof(int));
+		int *ptr = buf + size;
+		int *vars = NULL;
+		int *label_calls = NULL;
+		struct stack_frame_info *sfi = NULL;
+		while ((sfi = sl_next_stack_frame(sfi)) != NULL) {
+			switch (sfi->tag) {
+			case STACK_NEARCALL:
+				if (label_calls)
+					(*label_calls)++;
+				vars = --ptr;
+				break;
+			case STACK_FARCALL:
+				vars = --ptr;
+				label_calls = --ptr;
+				break;
+			case STACK_VARIABLE:
+				if (vars)
+					(*vars)++;
+				break;
+			}
+		}
+		// Note that only the first `size` byte of the `size` words data is
+		// written, so information is lost.
+		fwrite(ptr, size, 1, fp);
+		fwrite(&size, 4, 1, fp);
+		free(buf);
+		fputs("INFS", fp);
+	}
+
 	fclose(fp);
 	scheduleSync();
 	free(save_base);
@@ -546,9 +631,9 @@ int save_saveAll(int no) {
 }
 
 /* スタック情報のセーブ */
-static int saveStackInfo(FILE *fp) {
+static int saveStackInfo(enum save_format format, FILE *fp) {
 	int size;
-	uint8_t *data = sl_saveStack(&size);
+	uint8_t *data = sl_saveStack(format, &size);
 
 	Ald_stackHdr head = { .size = size };
 	fwrite(&head, sizeof(head), 1, fp);
@@ -559,22 +644,22 @@ static int saveStackInfo(FILE *fp) {
 }
 
 /* スタック情報のロード */
-static void loadStackInfo(char *buf) {
+static void loadStackInfo(enum save_format format, char *buf) {
 	Ald_stackHdr *head = (Ald_stackHdr *)buf;
 	uint8_t *data = buf + sizeof(Ald_stackHdr);
-	sl_loadStack(data, head->size);
+	sl_loadStack(format, data, head->size);
 }
 
 /* 文字列変数のセーブ */
-static void *saveStrVar(Ald_strVarHdr *head) {
+static void *saveStrVar(enum save_format format, Ald_strVarHdr *head) {
 	int bufsize = 65536;
 	char *buf = malloc(bufsize);
 	if (!buf)
 		NOMEMERR();
 
+	const int base = format == SAVEFMT_XSYS35 ? 1 : 0;
 	int offset = 0;
-	// Do not save svar[0], for backward compatibility.
-	for (int i = 1; i <= svar_maxindex(); i++) {
+	for (int i = base; i <= svar_maxindex(); i++) {
 		const char *s = svar_get(i);
 		int len = strlen(s);
 		if (offset + len + 1 > bufsize) {
@@ -588,24 +673,24 @@ static void *saveStrVar(Ald_strVarHdr *head) {
 		offset += len + 1;
 	}
 	head->size   = offset;
-	head->count  = svar_maxindex();
-	head->maxlen = 101;  // so that old versions of xystem35 can read this save file
+	head->count  = svar_maxindex() + (1 - base);
+	head->maxlen = (format == SAVEFMT_XSYS35 ? 101 : 0);  // so that old versions of xystem35 can read this save file
 	return buf;
 }
 
 /* 文字列変数のロード */
-static void loadStrVar(char *buf) {
+static void loadStrVar(enum save_format format, char *buf) {
 	Ald_strVarHdr *head = (Ald_strVarHdr *)buf;
-	int cnt, max, i;
+	const int base = format == SAVEFMT_XSYS35 ? 1 : 0;
 	
-	cnt = head->count;
-	if (svar_maxindex() != cnt) {
-		WARNING("Unexpected number of strings in savedata (%d, expected %d)", cnt, svar_maxindex());
-		svar_init(cnt);
+	int cnt = head->count;
+	if ((1 - base) + svar_maxindex() != cnt) {
+		WARNING("Unexpected number of strings in savedata (%d, expected %d)", cnt, (1 - base) + svar_maxindex());
+		svar_init(format == SAVEFMT_XSYS35 ? cnt : cnt - 1);
 	}
 	buf += sizeof(Ald_strVarHdr);
-	for (i = 1; i <= cnt; i++) {
-		svar_set(i, buf);
+	for (int i = 0; i < cnt; i++) {
+		svar_set(i + base, buf);
 		buf += strlen(buf) + 1;
 	}
 }
diff --git a/src/savedata.h b/src/savedata.h
index 01fbf34..0862345 100644
--- a/src/savedata.h
+++ b/src/savedata.h
@@ -36,8 +36,15 @@
 #define SAVE_SAVEOK1      1
 #define SAVE_SAVEOK0      0
 
+enum save_format {
+	SAVEFMT_XSYS35,
+	SAVEFMT_SYS36,  // System3.5 v2.x - System3.6
+	SAVEFMT_SYS38,  // System3.8 - System3.9
+};
+
 struct VarRef;
 
+int save_setFormat(const char *format_name);
 int save_loadAll(int no);
 int save_saveAll(int no);
 int save_loadPartial(int no, struct VarRef *vref, int cnt);
diff --git a/src/scenario.c b/src/scenario.c
index e1b06ca..bd58596 100644
--- a/src/scenario.c
+++ b/src/scenario.c
@@ -381,9 +381,16 @@ struct save_stack_frame *push_save_stack_frame(int size, struct save_stack_frame
 	return f;
 }
 
-// Serialize the stack to the xsystem35 savedata format (i.e. the stack format
-// used in old versions of xsystem35).
-uint8_t *sl_saveStack(int *size_out) {
+uint8_t *sl_saveStack(enum save_format format, int *size_out) {
+	if (format != SAVEFMT_XSYS35) {
+		int size = stack_top - stack_buf;
+		uint8_t *buf = malloc(size);
+		memcpy(buf, stack_buf, size);
+		*size_out = size;
+		return buf;
+	}
+
+	// Serialize to the stack format used in old versions of xsystem35.
 	struct save_stack_frame *frame = NULL;
 	uint8_t *sp = stack_top;
 	while (sp > stack_buf) {
@@ -487,7 +494,7 @@ uint8_t *sl_saveStack(int *size_out) {
 		uint8_t *orig_stack = malloc(orig_size);
 		memcpy(orig_stack, stack_buf, orig_size);
 
-		sl_loadStack((uint8_t *)buf, *size_out);
+		sl_loadStack(format, (uint8_t *)buf, *size_out);
 
 		if (stack_top - stack_buf != orig_size || memcmp(stack_buf, orig_stack, orig_size)) {
 			FILE *fp = fopen("orig_stack", "wb");
@@ -503,18 +510,31 @@ uint8_t *sl_saveStack(int *size_out) {
 	return (uint8_t *)buf;
 }
 
-// Deserialize the stack from the xsystem35 savedata format.
-void sl_loadStack(uint8_t *unaligned_data, int size) {
+void sl_loadStack(enum save_format format, uint8_t *unaligned_data, int size) {
+	if (format != SAVEFMT_XSYS35) {
+		if (size > stack_size) {
+			while (size > stack_size)
+				stack_size *= 2;
+			free(stack_buf);
+			stack_buf = malloc(stack_size);
+			if (!stack_buf)
+				NOMEMERR();
+		}
+		memcpy(stack_buf, unaligned_data, size);
+		stack_top = stack_buf + size;
+		return;
+	}
+
+	// Deserialize from the stack format used in old versions of xsystem35.
 	int *data = malloc(size);
 	memcpy(data, unaligned_data, size);
 	struct save_stack_frame *frame = NULL;
 
 	for (int *p = data + size / sizeof(int); p > data;) {
-		int type = *--p;
-		int len = *--p;
+		int len = p[-2] + 2;
 		p -= len;
-		frame = push_save_stack_frame(len + 2, frame);
-		memcpy(frame->buf, p, (len + 2) * sizeof(int));
+		frame = push_save_stack_frame(len, frame);
+		memcpy(frame->buf, p, len * sizeof(int));
 	}
 	free(data);
 
diff --git a/src/scenario.h b/src/scenario.h
index 1ea501f..c45072f 100644
--- a/src/scenario.h
+++ b/src/scenario.h
@@ -27,6 +27,7 @@
 #include "portab.h"
 #include "system.h"
 
+enum save_format;
 struct VarRef;
 
 // Stack frame tags. Changing these will break savedata compatibility.
@@ -86,8 +87,8 @@ void sl_returnGoto(int address);
 void sl_clearStack(bool restore);
 void sl_pushVar(struct VarRef *vref, int cnt);
 void sl_popVar(struct VarRef *vref, int cnt);
-uint8_t *sl_saveStack(int *size);
-void sl_loadStack(uint8_t *data, int size);
+uint8_t *sl_saveStack(enum save_format format, int *size);
+void sl_loadStack(enum save_format format, uint8_t *data, int size);
 void sl_getStackInfo(struct stack_info *info);
 void sl_pushTextColor(uint8_t type, uint8_t color);
 void sl_pushTextSize(uint8_t type, int size);
diff --git a/src/xsystem35.c b/src/xsystem35.c
index 080f4f6..e373445 100644
--- a/src/xsystem35.c
+++ b/src/xsystem35.c
@@ -109,46 +109,47 @@ static void sys35_usage(boolean verbose) {
 	}
 	puts("Usage: xsystem35 [OPTIONS]\n");
 	puts("OPTIONS");
-	puts(" -gamefile file : set game resource file to 'file'");
-	puts(" -game     game : enable game-specific hacks");
-	puts(" -renderer name : set rendering driver name to 'name'");
-	puts(" -devcd device  : set cdrom device name to 'device'");
-	puts(" -devmidi device: set midi device name to 'device'");
+	puts(" -gamefile file  : set game resource file to 'file'");
+	puts(" -game game      : enable game-specific hacks");
+	puts(" -saveformat fmt : save file format. 'xsystem35' (default), 'system36' or 'system39'");
+	puts(" -renderer name  : set rendering driver name to 'name'");
+	puts(" -devcd device   : set cdrom device name to 'device'");
+	puts(" -devmidi device : set midi device name to 'device'");
 	
-	puts(" -M?            : select output midi methos");
+	puts(" -M?             : select output midi methos");
 #ifdef ENABLE_MIDI_SDLMIXER
-	puts(" -Me            : SDL_mixer midi player");
+	puts(" -Me             : SDL_mixer midi player");
 #endif
 #ifdef ENABLE_MIDI_RAWMIDI
-	puts(" -Mr            : Raw Midi device");
+	puts(" -Mr             : Raw Midi device");
 #endif
 #ifdef ENABLE_MIDI_SEQMIDI
-	puts(" -Ms?           : Sequenceer device (?:devicenumber)");
+	puts(" -Ms?            : Sequenceer device (?:devicenumber)");
 #endif
 #ifdef ENABLE_MIDI_PORTMIDI
-	puts(" -Mp?           : ALSA (via PortMidi) (?:devicenumber)");
+	puts(" -Mp?            : ALSA (via PortMidi) (?:devicenumber)");
 #endif
-	puts(" -M0            : Disable MIDI output");
+	puts(" -M0             : Disable MIDI output");
 	
-	puts(" -devjoy device : joystick device index (0-)");
+	puts(" -devjoy device  : joystick device index (0-)");
 
-	puts(" -ttfont_mincho: set TrueType font for mincho");
-	puts(" -ttfont_gothic: set TrueType font for mincho");
+	puts(" -ttfont_mincho  : set TrueType font for mincho");
+	puts(" -ttfont_gothic  : set TrueType font for mincho");
 	
 #ifdef DEBUG
-	puts(" -debuglv #     : debug level");
-	puts("                :  1: warings");
-	puts("                :  2: unimplemented commands");
-	puts("                :  5: command trace");
-	puts("                :  6: message trace");
+	puts(" -debuglv #      : debug level");
+	puts("                 :  1: warings");
+	puts("                 :  2: unimplemented commands");
+	puts("                 :  5: command trace");
+	puts("                 :  6: message trace");
 #endif  
-	puts(" -noantialias   : never use antialiased string");
-	puts(" -fullscreen    : start with fullscreen");
-	puts(" -integerscale  : use integer scaling when resizing");
-	puts(" -noimagecursor : disable image cursor");
-	puts(" -version       : show version");
-	puts(" -h             : show this message");
-	puts(" --help         : show this message");
+	puts(" -noantialias    : never use antialiased string");
+	puts(" -fullscreen     : start with fullscreen");
+	puts(" -integerscale   : use integer scaling when resizing");
+	puts(" -noimagecursor  : disable image cursor");
+	puts(" -version        : show version");
+	puts(" -h              : show this message");
+	puts(" --help          : show this message");
 	exit(1);
 }
 
@@ -315,6 +316,10 @@ static void sys35_ParseOption(int *argc, char **argv) {
 			if (argv[i + 1] != NULL) {
 				enable_hack_by_gameid(argv[i + 1]);
 			}
+		} else if (0 == strcmp(argv[i], "-saveformat")) {
+			if (argv[i + 1] != NULL) {
+				save_setFormat(argv[i + 1]);
+			}
 		}
 	}
 }
@@ -404,6 +409,11 @@ static void check_profile() {
 	if (param) {
 		enable_hack_by_gameid(param);
 	}
+	/* Save file format */
+	param = get_profile("saveformat");
+	if (param) {
+		save_setFormat(param);
+	}
 }
 
 #ifdef HAVE_SIGACTION
diff --git a/xsys35rc.sample b/xsys35rc.sample
index 0cb0686..179ead8 100644
--- a/xsys35rc.sample
+++ b/xsys35rc.sample
@@ -30,6 +30,16 @@
 
 # ------------------------------------------------------------
 
+# ------------------------------------------------------------
+# The format when writing save files.
+#  xsystem35 : default
+#  system36  : compatible with System3.5 v2 - System3.6
+#  system39  : compatible with System3.8 - System3.9
+
+#saveformat: xsystem35
+
+# ------------------------------------------------------------
+
 # ------------------------------------------------------------
 # CD-ROM のデバイス名
 #