diff --git a/command.c b/command.c
index 1f3003020f..2e3056ed6a 100644
--- a/command.c
+++ b/command.c
@@ -321,8 +321,6 @@ int32 DoCommandByTile(TileIndex tile, uint32 p1, uint32 p2, uint32 flags, uint p
 }
 
 
-//extern void _stdcall Sleep(int s);
-
 int32 DoCommand(int x, int y, uint32 p1, uint32 p2, uint32 flags, uint procc)
 {
 	int32 res;
diff --git a/engine.c b/engine.c
index 47e5a6e93e..e35085b428 100644
--- a/engine.c
+++ b/engine.c
@@ -647,8 +647,6 @@ uint16 GetCallBackResult(uint16 callback_info, byte engine, const Vehicle *v)
 static byte _vsg_random_triggers;
 static byte _vsg_bits_to_reseed;
 
-extern int _custom_sprites_base;
-
 static SpriteGroup *TriggerVehicleSpriteGroup(SpriteGroup *spritegroup,
 	Vehicle *veh, uint16 callback_info, resolve_callback resolve_func)
 {
diff --git a/gfx.c b/gfx.c
index db64cb0494..c404c608a6 100644
--- a/gfx.c
+++ b/gfx.c
@@ -1729,8 +1729,6 @@ static void DbgScreenRect(int left, int top, int right, int bottom)
 }
 #endif
 
-extern bool _dbg_screen_rect;
-
 void RedrawScreenRect(int left, int top, int right, int bottom)
 {
 	assert(right <= _screen.width && bottom <= _screen.height);
diff --git a/intro_gui.c b/intro_gui.c
index 26180c6c7b..299393f2dd 100644
--- a/intro_gui.c
+++ b/intro_gui.c
@@ -16,10 +16,6 @@
 
 extern void SwitchMode(int new_mode);
 
-#if 0
-static void ShowSelectTutorialWindow() {}
-#endif
-
 static const Widget _select_game_widgets[] = {
 {    WWT_CAPTION, RESIZE_NONE, 13,   0, 335,   0,  13, STR_0307_OPENTTD,       STR_NULL},
 {     WWT_IMGBTN, RESIZE_NONE, 13,   0, 335,  14, 196, STR_NULL,               STR_NULL},
diff --git a/main_gui.c b/main_gui.c
index 852ccb51ef..3c7ba99f0b 100644
--- a/main_gui.c
+++ b/main_gui.c
@@ -36,9 +36,6 @@
 static const uint MinDate = 0;     // 1920-01-01 (MAX_YEAR_BEGIN_REAL)
 static const uint MaxDate = 29220; // 2000-01-01
 
-extern void DoTestSave(void);
-extern void DoTestLoad(void);
-
 static int _rename_id;
 static int _rename_what;
 
diff --git a/network_server.c b/network_server.c
index 86743e758d..c6aa17f637 100644
--- a/network_server.c
+++ b/network_server.c
@@ -27,8 +27,6 @@ void NetworkHandleCommandQueue(NetworkClientState *cs);
 void NetworkPopulateCompanyInfo(void);
 void NetworkSendPatchSettings(NetworkClientState *cs);
 
-extern const char _openttd_revision[];
-
 // Is the network enabled?
 
 // **********
diff --git a/newgrf.c b/newgrf.c
index 62223d8860..45ef6999b9 100644
--- a/newgrf.c
+++ b/newgrf.c
@@ -35,7 +35,6 @@ GRFFile *_first_grffile;
 int _grffile_count;
 static int _cur_spriteid;
 static int _cur_stage;
-extern uint16 _custom_sprites_base;
 
 static int32 _paramlist[0x7f];
 static int _param_max;
diff --git a/openttd.c b/openttd.c
index bf4984e335..2b453693c3 100644
--- a/openttd.c
+++ b/openttd.c
@@ -62,9 +62,6 @@ extern void ShowOSErrorBox(const char *buf);
 
 bool LoadSavegame(const char *filename);
 
-extern void HalGameLoop(void);
-
-uint32 _pixels_redrawn;
 bool _dbg_screen_rect;
 
 /* TODO: usrerror() for errors which are not of an internal nature but
diff --git a/players.c b/players.c
index 26f872070c..5727ce353d 100644
--- a/players.c
+++ b/players.c
@@ -27,8 +27,6 @@
 
 PlayerID _current_player;
 
-extern void StartupEconomy(void);
-
 static const SpriteID cheeks_table[4] = {
 	0x325, 0x326,
 	0x390, 0x3B0,
@@ -458,8 +456,6 @@ restart:;
 	}
 }
 
-extern int GetPlayerMaxRailtype(int p);
-
 static Player *AllocatePlayer(void)
 {
 	Player *p;
diff --git a/video/sdl_v.c b/video/sdl_v.c
index 0ff082f172..4e7b36ab15 100644
--- a/video/sdl_v.c
+++ b/video/sdl_v.c
@@ -25,8 +25,6 @@ static int _num_dirty_rects;
 
 static void SdlVideoMakeDirty(int left, int top, int width, int height)
 {
-//	printf("(%d,%d)-(%d,%d)\n", left, top, width, height);
-//	_pixels_redrawn += width*height;
 	if (_num_dirty_rects < MAX_DIRTY_RECTS) {
 		_dirty_rects[_num_dirty_rects].x = left;
 		_dirty_rects[_num_dirty_rects].y = top;
diff --git a/window.c b/window.c
index 3f6958724d..e51b07a72a 100644
--- a/window.c
+++ b/window.c
@@ -1492,8 +1492,6 @@ void InputLoop(void)
 
 static int _we4_timer;
 
-extern uint32 _pixels_redrawn;
-
 void UpdateWindows(void)
 {
 	Window *w;