Salicylazosulphapyridine and corticosteroids are the only remedies for inflammatory bowel disease currently in clinical use. They do not, however, necessarily bring about satisfactory therapeutic benefits, so that new agents are needed. In this study, we evaluated the effect of bucillamine, a new antirheumatic agent, in experimental rat colitis induced by trinitrobenzene sulfonic acid enema. Wistar rats were given vehicle alone (n = 16) or treated with 50 (n = 20) or 150 (n = 20) mg/kg of bucillamine daily for three weeks after induction of colitis. Conventional histological sections of the colon stained by haematoxylin and eosin were prepared and observed under a light microscope to determine colonic damage scores. The determinations were significantly lower in the group treated with 50 mg/kg of bucillamine and tended to be lower in the group treated with 150 mg/kg of bucillamine than in the untreated group, which implied that the experimentally induced colonic inflammatory changes and ulcerations were alleviated by bucillamine. Blood tests showed no abnormal values at the end of the treatment. The present observations suggest that bucillamine should be developed further as a possible therapy for inflammatory bowel disease.