diff --git a/DiabloUI/diabloui.h b/DiabloUI/diabloui.h
index ec1e004b2..b89796754 100644
--- a/DiabloUI/diabloui.h
+++ b/DiabloUI/diabloui.h
@@ -32,7 +32,7 @@ void __stdcall UiInitialize();
 BOOL __stdcall UiCopyProtError(int *pdwResult);
 void __stdcall UiAppActivate(BOOL bActive);
 BOOL __fastcall UiValidPlayerName(char *name); /* check __stdcall */
-BOOL __stdcall UiSelHeroMultDialog(BOOL(__stdcall *fninfo)(BOOL(__stdcall *fninfofunc)(_uiheroinfo *)), BOOL(__stdcall *fncreate)(_uiheroinfo *), BOOL(__stdcall *fnremove)(_uiheroinfo *), BOOL(__stdcall *fnstats)(unsigned int, _uidefaultstats *), int *dlgresult, int *a6, char *name);
+BOOL __stdcall UiSelHeroMultDialog(BOOL(__stdcall *fninfo)(BOOL(__stdcall *fninfofunc)(_uiheroinfo *)), BOOL(__stdcall *fncreate)(_uiheroinfo *), BOOL(__stdcall *fnremove)(_uiheroinfo *), BOOL(__stdcall *fnstats)(unsigned int, _uidefaultstats *), int *dlgresult, BOOL *hero_is_created, char *name);
 BOOL __stdcall UiSelHeroSingDialog(BOOL(__stdcall *fninfo)(BOOL(__stdcall *fninfofunc)(_uiheroinfo *)), BOOL(__stdcall *fncreate)(_uiheroinfo *), BOOL(__stdcall *fnremove)(_uiheroinfo *), BOOL(__stdcall *fnstats)(unsigned int, _uidefaultstats *), int *dlgresult, char *name, int *difficulty);
 BOOL __stdcall UiCreditsDialog(int a1);
 BOOL __stdcall UiMainMenuDialog(char *name, int *pdwResult, void(__stdcall *fnSound)(char *file), int a4);
diff --git a/Source/appfat.h b/Source/appfat.h
index 144870f07..8a6724f81 100644
--- a/Source/appfat.h
+++ b/Source/appfat.h
@@ -3,7 +3,7 @@
 #define __APPFAT_H__
 
 extern char sz_error_buf[256];
-extern int terminating;
+extern BOOL terminating;
 extern int cleanup_thread_id;
 
 void TriggerBreak();
diff --git a/Source/diablo.cpp b/Source/diablo.cpp
index ae6a6a956..2617de163 100644
--- a/Source/diablo.cpp
+++ b/Source/diablo.cpp
@@ -456,7 +456,7 @@ void diablo_parse_flags(char *args)
 				debug_mode_key_w = 1;
 				break;
 			case 'x':
-				fullscreen = 0;
+				fullscreen = FALSE;
 				break;
 			}
 #endif
diff --git a/Source/doom.h b/Source/doom.h
index 460a4e7ec..31635fe0e 100644
--- a/Source/doom.h
+++ b/Source/doom.h
@@ -5,7 +5,7 @@
 extern int doom_quest_time;
 extern int doom_stars_drawn;
 extern BYTE *pDoomCel;
-extern int doomflag;
+extern BOOL doomflag;
 extern int DoomQuestState;
 
 /*
diff --git a/Source/items.cpp b/Source/items.cpp
index c69673faf..991d09353 100644
--- a/Source/items.cpp
+++ b/Source/items.cpp
@@ -1750,7 +1750,7 @@ void GetItemPower(int i, int minlvl, int maxlvl, int flgs, BOOL onlygood)
 		CalcItemValue(i);
 }
 
-void GetItemBonus(int i, int idata, int minlvl, int maxlvl, int onlygood)
+void GetItemBonus(int i, int idata, int minlvl, int maxlvl, BOOL onlygood)
 {
 	if (item[i]._iClass != ICLASS_GOLD) {
 		if (minlvl > 25)
diff --git a/Source/items.h b/Source/items.h
index 7ca3bb78a..af0996627 100644
--- a/Source/items.h
+++ b/Source/items.h
@@ -44,7 +44,7 @@ void GetItemAttrs(int i, int idata, int lvl);
 int RndPL(int param1, int param2);
 int PLVal(int pv, int p1, int p2, int minv, int maxv);
 void SaveItemPower(int i, int power, int param1, int param2, int minval, int maxval, int multval);
-void GetItemPower(int i, int minlvl, int maxlvl, int flgs, int onlygood);
+void GetItemPower(int i, int minlvl, int maxlvl, int flgs, BOOL onlygood);
 void GetItemBonus(int i, int idata, int minlvl, int maxlvl, BOOL onlygood);
 void SetupItem(int i);
 int RndItem(int m);
diff --git a/Source/monster.cpp b/Source/monster.cpp
index 36f0422ce..fcce5c0f4 100644
--- a/Source/monster.cpp
+++ b/Source/monster.cpp
@@ -1866,7 +1866,7 @@ void M_ChangeLightOffset(int monst)
 	ChangeLightOff(monster[monst].mlid, _mxoff, _myoff * (ly >> 3));
 }
 
-int M_DoStand(int i)
+BOOL M_DoStand(int i)
 {
 	MonsterStruct *Monst;
 
diff --git a/Source/msg.cpp b/Source/msg.cpp
index a8d427f11..0f4387873 100644
--- a/Source/msg.cpp
+++ b/Source/msg.cpp
@@ -109,7 +109,7 @@ void msg_free_packets()
 
 int msg_wait_for_turns()
 {
-	int received;
+	BOOL received;
 	DWORD turns;
 
 	if (!sgbDeltaChunks) {
diff --git a/Source/multi.cpp b/Source/multi.cpp
index 543650360..dcf954101 100644
--- a/Source/multi.cpp
+++ b/Source/multi.cpp
@@ -301,7 +301,8 @@ void multi_net_ping()
 
 int multi_handle_delta()
 {
-	int i, received;
+	int i;
+	BOOL received;
 
 	if (gbGameDestroyed) {
 		gbRunGame = FALSE;
@@ -850,7 +851,7 @@ BOOL multi_init_single(_SNETPROGRAMDATA *client_info, _SNETPLAYERDATA *user_info
 	return TRUE;
 }
 
-BOOL multi_init_multi(_SNETPROGRAMDATA *client_info, _SNETPLAYERDATA *user_info, _SNETUIDATA *ui_info, int *pfExitProgram)
+BOOL multi_init_multi(_SNETPROGRAMDATA *client_info, _SNETPLAYERDATA *user_info, _SNETUIDATA *ui_info, BOOL *pfExitProgram)
 {
 	BOOL first;
 	int playerId;
@@ -889,7 +890,7 @@ BOOL multi_init_multi(_SNETPROGRAMDATA *client_info, _SNETPLAYERDATA *user_info,
 	}
 }
 
-BOOL multi_upgrade(int *pfExitProgram)
+BOOL multi_upgrade(BOOL *pfExitProgram)
 {
 	BOOL result;
 	int status;
diff --git a/Source/multi.h b/Source/multi.h
index dc4fd6e41..f02eea783 100644
--- a/Source/multi.h
+++ b/Source/multi.h
@@ -51,8 +51,8 @@ void multi_send_pinfo(int pnum, char cmd);
 int InitLevelType(int l);
 void SetupLocalCoords();
 BOOL multi_init_single(_SNETPROGRAMDATA *client_info, _SNETPLAYERDATA *user_info, _SNETUIDATA *ui_info);
-BOOL multi_init_multi(_SNETPROGRAMDATA *client_info, _SNETPLAYERDATA *user_info, _SNETUIDATA *ui_info, int *pfExitProgram);
-BOOL multi_upgrade(int *pfExitProgram);
+BOOL multi_init_multi(_SNETPROGRAMDATA *client_info, _SNETPLAYERDATA *user_info, _SNETUIDATA *ui_info, BOOL *pfExitProgram);
+BOOL multi_upgrade(BOOL *pfExitProgram);
 void recv_plrinfo(int pnum, TCmdPlrInfoHdr *p, BOOL recv);
 
 /* rdata */
diff --git a/Source/nthread.cpp b/Source/nthread.cpp
index 0d6f47877..53cacc3ed 100644
--- a/Source/nthread.cpp
+++ b/Source/nthread.cpp
@@ -171,7 +171,7 @@ void nthread_start(BOOL set_turn_upper_bit)
 unsigned int __stdcall nthread_handler(void *)
 {
 	int delta;
-	int received;
+	BOOL received;
 
 	if (nthread_should_run) {
 		while (1) {