diff --git a/ij/gui/Roi.java b/ij/gui/Roi.java
index 4d5e76016..61d5c4703 100644
--- a/ij/gui/Roi.java
+++ b/ij/gui/Roi.java
@@ -55,6 +55,7 @@ public class Roi extends Object implements Cloneable, java.io.Serializable, Iter
 	public static final int FERET_ARRAYSIZE = 16; // Size of array with Feret values
 	public static final int FERET_ARRAY_POINTOFFSET = 8; // Where point coordinates start in Feret array
 	private static final String NAMES_KEY = "group.names";
+	private static final int MAX_ROI_GROUP = 65535; // limit to uint16 max value
 
 	static final int NO_MODS=0, ADD_TO_ROI=1, SUBTRACT_FROM_ROI=2; // modification states
 
@@ -1807,7 +1808,7 @@ public static int getDefaultGroup() {
 	 * @see #getGroupColor
 	*/
 	public static void setDefaultGroup(int group) {
-		if (group<0 || group>255)
+		if (group<0 || group>MAX_ROI_GROUP)
 			throw new IllegalArgumentException("Invalid group: "+group);
 		defaultGroup = group;
 		groupColor = getGroupColor(group);
@@ -1820,7 +1821,7 @@ public int getGroup() {
 
 	/** Returns the group name associtated with the specified group. */
 	public static String getGroupName(int groupNumber) {
-		if (groupNumber<1 || groupNumber>255)
+		if (groupNumber<1 || groupNumber>MAX_ROI_GROUP)
 			return null;
 		if (groupNames==null && groupNamesString==null)
 			return null;
@@ -1835,7 +1836,7 @@ public static String getGroupName(int groupNumber) {
 	}
 
 	public static synchronized void setGroupName(int groupNumber, String name) {
-		if (groupNumber<1 || groupNumber>255)
+		if (groupNumber<1 || groupNumber>MAX_ROI_GROUP)
 			return;
 		if (groupNamesString==null && groupNames==null)
 			groupNames = new String[groupNumber];
@@ -1884,7 +1885,7 @@ public static void setGroupNames(String names) {
 
 	/** Sets the group of this Roi, and updates stroke color accordingly. */
 	public void setGroup(int group) {
-		if (group<0 || group>255)
+		if (group<0 || group>MAX_ROI_GROUP)
 			throw new IllegalArgumentException("Invalid group: "+group);
 		if (group>0)
 			setStrokeColor(getGroupColor(group));
diff --git a/ij/io/RoiDecoder.java b/ij/io/RoiDecoder.java
index 2d989f008..9efc822c3 100644
--- a/ij/io/RoiDecoder.java
+++ b/ij/io/RoiDecoder.java
@@ -89,6 +89,7 @@ public class RoiDecoder {
 	public static final int ROI_PROPS_OFFSET = 40;
 	public static final int ROI_PROPS_LENGTH = 44;
 	public static final int COUNTERS_OFFSET = 48;
+	public static final int GROUP_EXTENDED = 52;  //short (uint16) for groups > 255
 
 	// subtypes
 	public static final int TEXT = 1;
@@ -207,7 +208,11 @@ public Roi getRoi() throws IOException {
 			overlayFontSize = getShort(hdr2Offset+OVERLAY_FONT_SIZE);
 			imageOpacity = getByte(hdr2Offset+IMAGE_OPACITY);
 			imageSize = getInt(hdr2Offset+IMAGE_SIZE);
-			group = getByte(hdr2Offset+GROUP);
+			int groupByte = getByte(hdr2Offset+GROUP);
+			if (version>=229 && groupByte==0 && hdr2Offset+GROUP_EXTENDED+2<=size)
+				group = getUnsignedShort(hdr2Offset+GROUP_EXTENDED);
+			else
+				group = groupByte;
 		}
 		
 		if (name!=null && name.endsWith(".roi"))
diff --git a/ij/io/RoiEncoder.java b/ij/io/RoiEncoder.java
index 745ba1197..9bf1e156f 100644
--- a/ij/io/RoiEncoder.java
+++ b/ij/io/RoiEncoder.java
@@ -15,7 +15,7 @@
 public class RoiEncoder {
 	static final int HEADER_SIZE = 64;
 	static final int HEADER2_SIZE = 64;
-	static final int VERSION = 228; // v1.52t (roi groups, scale stroke width)
+	static final int VERSION = 229; // v1.52u (extended roi groups via uint16)
 	private String path;
 	private OutputStream f;
 	private final int polygon=0, rect=1, oval=2, line=3, freeline=4, polyline=5, noRoi=6, freehand=7, 
@@ -423,7 +423,13 @@ void putHeader2(Roi roi, int hdr2Offset) {
 			putProps(roi, hdr2Offset);
 		if (countersSize>0)
 			putPointCounters(roi, hdr2Offset);
-		putByte(hdr2Offset+RoiDecoder.GROUP, roi.getGroup());
+		int group = roi.getGroup();
+		if (group > 255) {
+			putByte(hdr2Offset+RoiDecoder.GROUP, 0);  // marker for extended group
+			putShort(hdr2Offset+RoiDecoder.GROUP_EXTENDED, group);
+		} else {
+			putByte(hdr2Offset+RoiDecoder.GROUP, group);
+		}
 	}
 
 	void putName(Roi roi, int hdr2Offset) {