Two 6-yr-old male sibling Amur leopards (Panthera pardus orientalis) housed together at the Pittsburgh Zoo presented for acute onset of diarrhea with no changes in appetite or behavior. Heat-fixed modified Wright-stained and Gram-stained fecal smears revealed a mixed bacterial population with a large number of gram-positive Clostridium perfringens-like spores (>20 per high-power oil immersion field). In addition, C. perfringens enterotoxin was isolated from one leopard at 1:256, confirming the presence of C. perfringens enterotoxicosis. Treatment with oral metronidazole, tylosin tartrate, and psyllium fiber was prescribed, with return of more normal stool by the third day of treatment. Fecal consistency steadily improved and was considered normal by the time all prescribed treatments were complete. Diarrhea has not recurred. Partially thawed meat in the leopards' diet may have precipitated the production of an endogenous clostridial enterotoxicosis by disrupting digestive tract flora with resultant clostridial overgrowth and sporulation.