A 41-year-old man with rheumatoid arthritis developed severe acute hepatitis 3 days after starting cimetidine for duodenal ulcer. Other causes were ruled out and he recovered after cimetidine was discontinued. Mild transient elevations of hepatic enzymes have been reported in 3.6% of patients taking cimetidine. However, only 12 cases of severe acute hepatitis associated with cimetidine, mostly secondary to idiosyncrasy, have been reported in the English literature. This rare but serious complication of cimetidine should be kept in mind.