Antibiotic induced Clostridium colitis is a common problem of horses admitted into hospitals. Clostridial diarrhea has been associated with many factors that may alter the balance of intestinal flora, such as administration of antibiotics or withholding feed prior to surgery, but has also occurred in absence of any identifiable risk factors. This report describes a case of antibiotic induced Clostridium colitis post myelogram, including the sequela of the colitis and the treatment of the disease process. Differentials for post operative colitis are discussed as are diagnostics used to rule otu these differentials.