diff --git a/device.h b/device.h
index 2b11be2..0baea83 100644
--- a/device.h
+++ b/device.h
@@ -66,6 +66,7 @@ struct device_args {
 	int			vcc_mv;
 	const char		*path;
 	const char		*forced_chip_id;
+	const char		*requested_serial;
 };
 
 struct device_class {
diff --git a/fet.c b/fet.c
index 8845d39..730b2bb 100644
--- a/fet.c
+++ b/fet.c
@@ -1053,7 +1053,7 @@ static device_t fet_open_rf2500(const struct device_args *args)
 		return NULL;
 	}
 
-        trans = rf2500_open(args->path);
+        trans = rf2500_open(args->path, args->requested_serial);
         if (!trans)
                 return NULL;
 
@@ -1082,7 +1082,7 @@ static device_t fet_open_olimex(const struct device_args *args)
 	if (args->flags & DEVICE_FLAG_TTY)
 		trans = uif_open(args->path, UIF_TYPE_OLIMEX);
 	else
-		trans = olimex_open(args->path);
+		trans = olimex_open(args->path, args->requested_serial);
 
         if (!trans)
                 return NULL;
diff --git a/main.c b/main.c
index 2d259c3..7c05d1d 100644
--- a/main.c
+++ b/main.c
@@ -88,6 +88,8 @@ static void usage(const char *progname)
 "        Connect via the given tty device, rather than USB.\n"
 "    -U bus:dev\n"
 "        Specify a particular USB device to connect to.\n"
+"    -s serial\n"
+"        Specify a particular device serial number to connect to.\n"
 "    -j\n"
 "        Use JTAG, rather than Spy-Bi-Wire (UIF devices only).\n"
 "    -v voltage\n"
@@ -178,7 +180,7 @@ static int parse_cmdline_args(int argc, char **argv,
 	};
 	int want_usb = 0;
 
-	while ((opt = getopt_long(argc, argv, "d:jv:nU:q",
+	while ((opt = getopt_long(argc, argv, "d:jv:nU:s:q",
 				  longopts, NULL)) >= 0)
 		switch (opt) {
 		case 'q':
@@ -208,6 +210,10 @@ static int parse_cmdline_args(int argc, char **argv,
 			want_usb = 1;
 			break;
 
+		case 's':
+			args->devarg.requested_serial = optarg;
+			break;
+
 		case 'L':
 			exit(list_devices());
 
@@ -300,6 +306,7 @@ int main(int argc, char **argv)
 	opdb_reset();
 
 	args.devarg.vcc_mv = 3000;
+	args.devarg.requested_serial = NULL;
 	if (parse_cmdline_args(argc, argv, &args) < 0)
 		return -1;
 
diff --git a/mspdebug.man b/mspdebug.man
index 8c01181..23e0e1b 100644
--- a/mspdebug.man
+++ b/mspdebug.man
@@ -46,6 +46,9 @@ section \fBDRIVERS\fR below for details.
 .IP "\-U \fIbus\fR:\fIdevice\fR"
 Specify a particular USB device to connect to. Without this option,
 the first device of the appropriate type is opened.
+.IP "\-s \fIserial\fR"
+Specify a particular USB device serial number to connect to. Use this
+option to distinguish between multiple devices of the same type.
 .IP "\-n"
 Do not process the startup file (~/.mspdebug).
 .IP "\--long-password"
diff --git a/olimex.c b/olimex.c
index 4c61478..722ca67 100644
--- a/olimex.c
+++ b/olimex.c
@@ -221,7 +221,7 @@ static void usbtr_destroy(transport_t tr_base)
 	free(tr);
 }
 
-transport_t olimex_open(const char *devpath)
+transport_t olimex_open(const char *devpath, const char *requested_serial)
 {
 	struct olimex_transport *tr = malloc(sizeof(*tr));
 	struct usb_device *dev;
@@ -243,9 +243,11 @@ transport_t olimex_open(const char *devpath)
 	if (devpath) {
 		dev = usbutil_find_by_loc(devpath);
 	} else {
-		dev = usbutil_find_by_id(USB_FET_VENDOR, V1_PRODUCT);
+		dev = usbutil_find_by_id(USB_FET_VENDOR, V1_PRODUCT,
+					 requested_serial);
 		if (!dev)
-			dev = usbutil_find_by_id(USB_FET_VENDOR, V2_PRODUCT);
+			dev = usbutil_find_by_id(USB_FET_VENDOR, V2_PRODUCT,
+						 requested_serial);
 	}
 
 	if (!dev) {
diff --git a/olimex.h b/olimex.h
index 38f883f..fe4060c 100644
--- a/olimex.h
+++ b/olimex.h
@@ -28,6 +28,6 @@
  *
  * A particular USB device may be specified in bus:dev form.
  */
-transport_t olimex_open(const char *usb_device);
+transport_t olimex_open(const char *usb_device, const char *requested_serial);
 
 #endif
diff --git a/rf2500.c b/rf2500.c
index 50762f0..21bd2f1 100644
--- a/rf2500.c
+++ b/rf2500.c
@@ -179,7 +179,7 @@ static void usbtr_destroy(transport_t tr_base)
 	free(tr);
 }
 
-transport_t rf2500_open(const char *devpath)
+transport_t rf2500_open(const char *devpath, const char *requested_serial)
 {
 	struct rf2500_transport *tr = malloc(sizeof(*tr));
 	struct usb_device *dev;
@@ -201,7 +201,8 @@ transport_t rf2500_open(const char *devpath)
 	if (devpath)
 		dev = usbutil_find_by_loc(devpath);
 	else
-		dev = usbutil_find_by_id(USB_FET_VENDOR, USB_FET_PRODUCT);
+		dev = usbutil_find_by_id(USB_FET_VENDOR, USB_FET_PRODUCT,
+					 requested_serial);
 
 	if (!dev) {
 		free(tr);
diff --git a/rf2500.h b/rf2500.h
index e766624..a702102 100644
--- a/rf2500.h
+++ b/rf2500.h
@@ -27,6 +27,6 @@
  *
  * A particular device may be specified in bus:dev form.
  */
-transport_t rf2500_open(const char *dev_path);
+transport_t rf2500_open(const char *dev_path, const char *requested_serial);
 
 #endif
diff --git a/usbutil.c b/usbutil.c
index a0a514a..d03d72b 100644
--- a/usbutil.c
+++ b/usbutil.c
@@ -43,43 +43,78 @@ static const char *device_help(const struct usb_device *dev)
 	return "";
 }
 
+static int read_serial(struct usb_device *dev, char *buf, int max_len)
+{
+	struct usb_dev_handle *dh = usb_open(dev);
+
+	if (!dh)
+		return -1;
+
+	if (usb_get_string_simple(dh, dev->descriptor.iSerialNumber,
+				  buf, max_len) < 0) {
+		usb_close(dh);
+		return -1;
+	}
+
+	usb_close(dh);
+	return 0;
+}
+
 void usbutil_list(void)
 {
 	const struct usb_bus *bus;
 
 	for (bus = usb_get_busses(); bus; bus = bus->next) {
-		const struct usb_device *dev;
+		struct usb_device *dev;
 		int busnum = atoi(bus->dirname);
 
 		printc("Devices on bus %03d:\n", busnum);
 
 		for (dev = bus->devices; dev; dev = dev->next) {
 			int devnum = atoi(dev->filename);
+			char serial[128];
 
-			printc("    %03d:%03d %04x:%04x %s\n",
+			printc("    %03d:%03d %04x:%04x %s",
 			       busnum, devnum,
 			       dev->descriptor.idVendor,
 			       dev->descriptor.idProduct,
 			       device_help(dev));
+
+			if (!read_serial(dev, serial, sizeof(serial)))
+				printc(" [serial: %s]\n", serial);
+			else
+				printc("\n");
 		}
 	}
 }
 
-struct usb_device *usbutil_find_by_id(int vendor, int product)
+struct usb_device *usbutil_find_by_id(int vendor, int product, const char *requested_serial)
 {
 	struct usb_bus *bus;
 
 	for (bus = usb_get_busses(); bus; bus = bus->next) {
 		struct usb_device *dev;
 
-		for (dev = bus->devices; dev; dev = dev->next)
+		for (dev = bus->devices; dev; dev = dev->next) {
 			if (dev->descriptor.idVendor == vendor &&
-			    dev->descriptor.idProduct == product)
-				return dev;
+			    dev->descriptor.idProduct == product) {
+				char buf[128];
+
+				if (!requested_serial ||
+				    (!read_serial(dev, buf, sizeof(buf)) &&
+				     !strcasecmp(requested_serial, buf)))
+					return dev;
+			}
+		}
 	}
 
-	printc_err("usbutil: unable to find a device matching "
-		"%04x:%04x\n", vendor, product);
+	if(requested_serial)
+		printc_err("usbutil: unable to find device matching "
+			"%04x:%04x with serial %s\n", vendor, product,
+			requested_serial);
+	else
+		printc_err("usbutil: unable to find a device matching "
+			"%04x:%04x\n", vendor, product);
 
 	return NULL;
 }
diff --git a/usbutil.h b/usbutil.h
index 49960c1..3573ffc 100644
--- a/usbutil.h
+++ b/usbutil.h
@@ -25,7 +25,8 @@
 void usbutil_list(void);
 
 /* Search for the first device matching the given Vendor:Product */
-struct usb_device *usbutil_find_by_id(int vendor, int product);
+struct usb_device *usbutil_find_by_id(int vendor, int product,
+				      const char *requested_serial);
 
 /* Search for a device using a bus:dev location string */
 struct usb_device *usbutil_find_by_loc(const char *loc);