diff --git a/area.go b/area.go
index 4fca39a..63d4602 100644
--- a/area.go
+++ b/area.go
@@ -72,7 +72,9 @@ type AreaHandler interface {
 
 // MouseEvent contains all the information for a mous event sent by Area.Mouse.
 // Mouse button IDs start at 1, with 1 being the left mouse button, 2 being the middle mouse button, and 3 being the right mouse button.
-// If additional buttons are supported, they will be returned with 4 being the first additional button. The association between button numbers and physical buttons are system-defined.
+// If additional buttons are supported, they will be returned with 4 being the first additional button.
+// The association between button numbers and physical buttons are system-defined.
+// For example, on Windows, buttons 4 and 5 are mapped to what are internally referred to as "XBUTTON1" and "XBUTTON2", which often correspond to the dedicated back/forward navigation buttons on the sides of many mice.
 // (TODO find out if there's a way to query available button count)
 type MouseEvent struct {
 	// Pos is the position of the mouse in the Area at the time of the event.
diff --git a/area_windows.go b/area_windows.go
index 3cd1e75..a7ee44c 100644
--- a/area_windows.go
+++ b/area_windows.go
@@ -483,7 +483,12 @@ func areaMouseEvent(s *sysData, button uint, up bool, count uint, wparam _WPARAM
 	if button != 3 && (wparam & _MK_RBUTTON) != 0 {
 		me.Held = append(me.Held, 3)
 	}
-	// TODO XBUTTONs?
+	if button != 4 && (wparam & _MK_XBUTTON1) != 0 {
+		me.Held = append(me.Held, 4)
+	}
+	if button != 5 && (wparam & _MK_XBUTTON2) != 0 {
+		me.Held = append(me.Held, 5)
+	}
 	repaint := s.handler.Mouse(me)
 	if repaint {
 		repaintArea(s)
@@ -654,7 +659,18 @@ func areaWndProc(s *sysData) func(hwnd _HWND, uMsg uint32, wParam _WPARAM, lPara
 		case _WM_RBUTTONUP:
 			areaMouseEvent(s, 3, true, 0, wParam, lParam)
 			return 0
-		// TODO XBUTTONs?
+		case _WM_XBUTTONDOWN:
+			which := uint((wParam >> 16) & 0xFFFF) + 3		// values start at 1; we want them to start at 4
+			areaMouseEvent(s, which, false, 1, wParam, lParam)
+			return _LRESULT(_TRUE)		// XBUTTON messages are different!
+		case _WM_XBUTTONDBLCLK:
+			which := uint((wParam >> 16) & 0xFFFF) + 3
+			areaMouseEvent(s, which, false, 2, wParam, lParam)
+			return _LRESULT(_TRUE)
+		case _WM_XBUTTONUP:
+			which := uint((wParam >> 16) & 0xFFFF) + 3
+			areaMouseEvent(s, which, true, 0, wParam, lParam)
+			return _LRESULT(_TRUE)
 		case _WM_KEYDOWN:
 			areaKeyEvent(s, false, wParam, lParam)
 			return 0