diff --git a/ij/gui/ImageCanvas.java b/ij/gui/ImageCanvas.java
index d5c619f0c..14cf47c0e 100644
--- a/ij/gui/ImageCanvas.java
+++ b/ij/gui/ImageCanvas.java
@@ -1447,9 +1447,10 @@ void setRoiModState(MouseEvent e, Roi roi, int handle) {
 		int tool = Toolbar.getToolId();
 		if (tool>Toolbar.FREEROI && tool!=Toolbar.WAND && tool!=Toolbar.POINT)
 			{roi.modState = Roi.NO_MODS; return;}
-		if (e.isShiftDown())
+		if (e.isShiftDown()){
 			roi.modState = Roi.ADD_TO_ROI;
-		else if (e.isAltDown())
+			if (e.isAltDown()) roi.modState = Roi.KEEP_WITHIN_ROI;
+		}else if (e.isAltDown())
 			roi.modState = Roi.SUBTRACT_FROM_ROI;
 		else
 			roi.modState = Roi.NO_MODS;
diff --git a/ij/gui/Roi.java b/ij/gui/Roi.java
index 076e6ad90..4bf0bb278 100644
--- a/ij/gui/Roi.java
+++ b/ij/gui/Roi.java
@@ -55,7 +55,7 @@ public class Roi extends Object implements Cloneable, java.io.Serializable, Iter
 	public static final int FERET_ARRAY_POINTOFFSET = 8; // Where point coordinates start in Feret array
 	private static final String NAMES_KEY = "group.names";
 
-	static final int NO_MODS=0, ADD_TO_ROI=1, SUBTRACT_FROM_ROI=2; // modification states
+	static final int NO_MODS=0, ADD_TO_ROI=1, SUBTRACT_FROM_ROI=2, KEEP_WITHIN_ROI=3; // modification states
 
 	int startX, startY, x, y, width, height;
 	double startXD, startYD;
@@ -1615,9 +1615,11 @@ void modifyRoi() {
 			s2 = (ShapeRoi)this;
 		else
 			s2 = new ShapeRoi(this);
-		if (previousRoi.modState==ADD_TO_ROI)
+		if (previousRoi.modState==ADD_TO_ROI) {
 			s1.or(s2);
-		else
+		}else if(previousRoi.modState==KEEP_WITHIN_ROI){
+			s1.and(s2);
+		}else
 			s1.not(s2);
 		previousRoi.modState = NO_MODS;
 		Roi roi2 = s1.trySimplify();
@@ -1658,6 +1660,7 @@ public void update(boolean add, boolean subtract) {
 		if (previousRoi==null) return;
 		if (add) {
 			previousRoi.modState = ADD_TO_ROI;
+			if(subtract) previousRoi.modState = KEEP_WITHIN_ROI;
 			modifyRoi();
 		} else if (subtract) {
 			previousRoi.modState = SUBTRACT_FROM_ROI;