Lincomycin and its analogue, clindamycin, are capable of producing mild to severe colonic mucosal injury in humans (antibiotic associated colitis). Patients with the disorder may have severe diarrhoea, pseudomembranous plaques, confluent pseudomembranes, and/or a frank, diffuse haemorrhagic colitis. The present study was designed to assess the Golden Syrian hamster as an animal model for antibiotic associated colitis and to describe lesions seen in the animal model by light, transmission electron, and scanning electron microscopy. A colitis was produced in Golden Syrian hamsters by oral or parenteral administration of lincomycin, clindamycin, or N-demethyl clindamycin. Animals were killed at intervals and microscopic studies made of sequential morphological changes in the ileum, caecum, and colon. The microscopic lesions in the early stages of the disorder were abnormalities within the brush border, cellular oedema, and hyperaemia. Changes in the intracellular organelles were observed in more severely damaged epithelial cells. Epithelial hyperplasia resulted in the piling up of cells on the mucosal surfaces. In specimens with the most severe damage, complete loss of epithelium from the mucosal surface was observed. Pseudomembranous plaques were occasionally seen. Comparison of the clinical, gross, and histological features of the animal disease with the human disorder suggest that, although minor differences are present, the hamster model is suitable for experimental studies of antibiotic associated colitis.