As it was explained to me by Dr. Kawasaki, a green stool means the food moved quickly through the digestive system. It can be indicative of any number of problems or just a non-problematic occurance. If all you get is the one loose green stool I wouldn't worry. If it persists for a while you should be concerned. After you've had ferrets for a while you can sort of tell when you need to be concerned pretty easily. You also look for other signs of illness like lethergy and changes in eating habits. A change in foods is one of the causes of some looseness and greenness in the stool also. I imagine the good doctors around here might have something more to say though. bill and diane killian zen and the art of ferrets. [Posted in FML issue 1210]