diff --git a/args.cpp b/args.cpp
index 7e4afc2..aa4320d 100644
--- a/args.cpp
+++ b/args.cpp
@@ -1,5 +1,30 @@
 #include "header.h"
 
+int ParseNum(const char *arg, int &num, int &opts, int pcopt)
+{
+	char *end;
+
+	if(pcopt == MOVHORZPC) {
+		if(*arg == 'l') opts |= MOVLEFT, ++arg;
+		else if(*arg == 'r') opts |= MOVRIGHT, ++arg;
+	}
+	else if(pcopt == MOVVERTPC) {
+		if(*arg == 't') opts |= MOVTOP, ++arg;
+		else if(*arg == 'b') opts |= MOVBOTTOM, ++arg;
+	}
+	else if(pcopt == SIZWIDTHPC) {
+		if(*arg == 'l' || *arg == 'r') opts |= SIZLEFT, ++arg;
+	}
+	else if(pcopt == SIZHEIGHTPC) {
+		if(*arg == 't' || *arg == 'b') opts |= SIZTOP, ++arg;
+	}
+	num = strtol(arg, &end, 10);
+	if(end == arg) return(1);
+	if(*end == '%' && end[1] == '\0') opts |= pcopt;
+	else if(*end != '\0') return(1);
+	return(0);
+}
+
 void ParseArgs(int argc, char *argv[], struct ARGS *a)
 {
 	register int i;
@@ -23,6 +48,8 @@ void ParseArgs(int argc, char *argv[], struct ARGS *a)
 	*a->tasks = (TASK) 0;
 	a->listopts = 0;
 	a->actopts = 0;
+	a->movopts = 0;
+	a->sizopts = 0;
 	a->sleep = 0;
 	a->wait = 0;
 	a->wait_ms = -1;
@@ -99,10 +126,8 @@ void ParseArgs(int argc, char *argv[], struct ARGS *a)
 			// next two args MUST be the new left and top coords
 			//
 			if( (i+2) < argc) {
-				a->left = atoi(argv[++i]);
-				a->top = atoi(argv[++i]);
-				if( (!a->left) && lstrcmp(argv[i-1], "0") ) Quit(MOVERR);
-				if( (!a->top) && lstrcmp(argv[i], "0") ) Quit(MOVERR);
+				if(ParseNum(argv[++i], a->left, a->movopts, MOVHORZPC)) Quit(MOVERR);
+				if(ParseNum(argv[++i], a->top, a->movopts, MOVVERTPC)) Quit(MOVERR);
 				}
 			else Quit(MOVERR);
 			}
@@ -112,10 +137,8 @@ void ParseArgs(int argc, char *argv[], struct ARGS *a)
 			//
 			PushTask(a->tasks, SIZ);
 			if( (i+2) < argc) {
-				a->width = atoi(argv[++i]);
-				a->height = atoi(argv[++i]);
-				if( (!a->width) && lstrcmp(argv[i-1], "0") ) Quit(SIZERR);
-				if( (!a->height) && lstrcmp(argv[i], "0") ) Quit(SIZERR);
+				if(ParseNum(argv[++i], a->width, a->sizopts, SIZWIDTHPC)) Quit(SIZERR);
+				if(ParseNum(argv[++i], a->height, a->sizopts, SIZHEIGHTPC)) Quit(SIZERR);
 				}
 			else Quit(SIZERR);
 			}
@@ -312,7 +335,7 @@ void Quit(const int Err)
 //       --1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
 		"Memory allocation failed",											/* MEMERR 0 */
 		"/MOV command requires left and top arguments",						/* MOVERR 1 */
-		"/SIZ command requires width and height agrguments",				/* SIZERR 2 */
+		"/SIZ command requires width and height arguments",					/* SIZERR 2 */
 		"/REN command requires a new caption to be specified",				/* RENERR 3 */
 		"Unrecognized argument(s). Use CMDOW /? for help",					/* UNRARG 4 */
 		"Incompatible argument(s). Use CMDOW /? for help",					/* CONARG 5 */
diff --git a/header.h b/header.h
index c3b8753..eca63db 100644
--- a/header.h
+++ b/header.h
@@ -66,6 +66,22 @@ enum ACTOPTS {
 	DONTBLAMEME = 0x0001			/* Allows actions to be performed on more than one window */
 };
 
+enum MOVOPTS {
+	MOVLEFT 	= 0x0001,			/* Move relative to left of monitor */
+	MOVTOP		= 0x0002,			/* Move relative to top of monitor */
+	MOVRIGHT	= 0x0004,			/* Move relative to right of monitor */
+	MOVBOTTOM	= 0x0008,			/* Move relative to bottom of monitor */
+	MOVHORZPC	= 0x0010,			/* Horizontal move is percentage of monitor width */
+	MOVVERTPC	= 0x0020,			/* Vertical move is percentage of monitor height */
+};
+
+enum SIZOPTS {
+	SIZLEFT 	= 0x0001,			/* Size by moving left edge, not right */
+	SIZTOP		= 0x0002,			/* Size by moving top edge, not bottom */
+	SIZWIDTHPC	= 0x0004,			/* Size relative to monitor width */
+	SIZHEIGHTPC = 0x0008,			/* Size relative to monitor height */
+};
+
 struct ARGS {
 	char			*caption;		/* Caption to list, or operate on */
 	char			*newcapt;		/* New caption, used with /REN */
@@ -78,6 +94,8 @@ struct ARGS {
 	int 			actopts;		/* Options for actions upon selected windows */
 	int				left, top;		/* Holds coords for moving window */
 	int				width, height;	/* Used for resizing a window */
+	int 			movopts;		/* Options for moving a window */
+	int 			sizopts;		/* Options for sizing a window */
 	int 			sleep;			/* Sleep milliseconds */
 	int 			wait, wait_ms;	/* If waiting, and for how long */
 	char			*file;			/* File to open/run, used with /RUN */
diff --git a/help.cpp b/help.cpp
index 07a6bc9..55eb0d0 100644
--- a/help.cpp
+++ b/help.cpp
@@ -204,16 +204,21 @@ printf(
 		printf(
 		"  /MOV    Moves the specified window. The left and top arguments specify the\n"
 		"          new position of the left top corner of the window. For level one\n"
-		"          windows this is relative to the desktop, and for child windows this\n"
-		"          is relative to its parent window. Level one windows can be moved off\n"
-		"          the screen using negative coords or coords greater than the desktop\n"
-		"          size. You should not move a minimized or maximized window without\n"
-		"          first restoring it.\n"
+		"          windows this is relative to the desktop (or monitor, if prefixed with\n"
+		"          'l'eft/'r'ight or 't'op/'b'ottom, and/or suffixed with '%%', which\n"
+		"          moves to a percentage of the width or height), and for child windows\n"
+		"          this is relative to its parent window. Level one windows can be moved\n"
+		"          off the screen using negative coords or coords greater than the\n"
+		"          desktop size. You should not move a minimized or maximized window\n"
+		"          without first restoring it.\n"
 		"  /SIZ    Resizes the specified window. The width and height arguments specify\n"
-		"          the new absolute width and height. In general, windows cannot be made\n"
-		"          smaller using /SIZ than they could if using conventional methods. You\n"
-		"          should not resize a minimized or maximized window without first\n"
-		"          restoring it.\n");
+		"          the new absolute width and height, or as a percentage of the monitor\n"
+		"          or parent if suffixed with '%%'. Prefix width with 'l' or 'r' to move\n"
+		"          the left edge, preserving the right; prefix height with 't' or 'b' to\n"
+		"          move the top edge, preserving the bottom. In general, windows cannot\n"
+		"          be made smaller using /SIZ than they could if using conventional\n"
+		"          methods. You should not resize a minimized or maximized window\n"
+		"          without first restoring it.\n");
 		printf(
 		"  /CLS    Politely asks the specified window to close. Most applications will\n"
 		"          respond to this request, although some may display a message box\n"
diff --git a/wlist.cpp b/wlist.cpp
index af47bc9..cbbe58e 100644
--- a/wlist.cpp
+++ b/wlist.cpp
@@ -566,20 +566,59 @@ void RenWin(struct WLIST *w, struct ARGS *a)
 	return;
 }
 
+//
+// Retrieve the bounding rectangle of a window: the monitor's work area for a
+// top-level window; otherwise the parent's client area.
+//
+void GetBounds(struct WLIST *w, RECT &r)
+{
+	if(w->level > 1) {
+		GetClientRect(w->parent, &r);
+	}
+	else {
+		HMONITOR monitor = MonitorFromWindow(w->hwnd, MONITOR_DEFAULTTONEAREST);
+		MONITORINFO mi;
+		mi.cbSize = sizeof(mi);
+		GetMonitorInfo(monitor, &mi);
+		r = mi.rcWork;
+	}
+}
+
 //
 // Move window to new top left coords
 //
 void MovWin(struct WLIST *w, struct ARGS *a)
 {
-	MoveWindow(w->hwnd, a->left, a->top,	w->width, w->height, TRUE);
+	int left = a->left, top = a->top;
+	if(a->movopts) {
+		RECT r;
+		GetBounds(w, r);
+		if(a->movopts & MOVHORZPC) left = (r.right - r.left) * left / 100;
+		if(a->movopts & MOVLEFT) left += r.left;
+		if(a->movopts & MOVRIGHT) left = r.right - left - w->width;
+		if(a->movopts & MOVVERTPC) top = (r.bottom - r.top) * top / 100;
+		if(a->movopts & MOVTOP) top += r.top;
+		if(a->movopts & MOVBOTTOM) top = r.bottom - top - w->height;
+	}
+	MoveWindow(w->hwnd, left, top, w->width, w->height, TRUE);
 }
 
 //
-// Resize window, to new height and width
+// Resize window to new height and width
 //
 void SizWin(struct WLIST *w, struct ARGS *a)
 {
-	MoveWindow(w->hwnd, w->left, w->top, a->width, a->height, TRUE);
+	int left = w->left, top = w->top;
+	int width = a->width, height = a->height;
+	if(a->sizopts & (SIZWIDTHPC | SIZHEIGHTPC)) {
+		RECT r;
+		GetBounds(w, r);
+		if(a->sizopts & SIZWIDTHPC) width = (r.right - r.left) * width / 100;
+		if(a->sizopts & SIZHEIGHTPC) height = (r.bottom - r.top) * height / 100;
+	}
+	if(a->sizopts & SIZLEFT) left += w->width - width;
+	if(a->sizopts & SIZTOP) top += w->height - height;
+	MoveWindow(w->hwnd, left, top, width, height, TRUE);
 }
 
 //