diff --git a/Demo/tkinter/guido/brownian.py b/Demo/tkinter/guido/brownian.py
new file mode 100644
index 0000000..ec3dbef
--- /dev/null
+++ b/Demo/tkinter/guido/brownian.py
@@ -0,0 +1,44 @@
+# An example of a multi-threaded Tkinter program.
+
+from Tkinter import *
+import random
+import threading
+import time
+import sys
+
+WIDTH = 400
+HEIGHT = 300
+SIGMA = 10
+BUZZ = 2
+RADIUS = 2
+LAMBDA = 10
+FILL = 'red'
+
+def particle(canvas):
+    r = RADIUS
+    x = random.gauss(WIDTH/2.0, SIGMA)
+    y = random.gauss(HEIGHT/2.0, SIGMA)
+    p = canvas.create_oval(x-r, y-r, x+r, y+r, fill=FILL)
+    while 1:
+        dx = random.gauss(0, BUZZ)
+        dy = random.gauss(0, BUZZ)
+        try:
+            canvas.move(p, dx, dy)
+        except TclError:
+            break
+        dt = random.expovariate(LAMBDA)
+        time.sleep(dt)
+
+def main():
+    root = Tk()
+    canvas = Canvas(root, width=WIDTH, height=HEIGHT)
+    canvas.pack(fill='both', expand=1)
+    np = 30
+    if sys.argv[1:]:
+        np = int(sys.argv[1])
+    for i in range(np):
+        t = threading.Thread(target=particle, args=(canvas,))
+        t.start()
+    root.mainloop()
+
+main()