Cimetidine is a histamine H2-receptor antagonist. Widely it is prescribed, and then various side effects have been increasingly recognized. Acute renal failure as a result of acute interstitial nephritis is one of the most important adverse effect. We report a case of biopsy-proven acute interstitial nephritis following cimetidine therapy. Farther more, we review other reported cases of cimetidine-induced acute interstitial nephritis, and discuss the clinical features and a role of immunological mechanisms of these cimetidine-induced disorders. A 52-year-old woman was admitted because of fever and protenuria. A month before admission, she developed gastric ulcer and was given cimetidine 600mg orally a day by a near physician. Laboratory data on admission included the following: white blood cell count, 14700/microliters; eosinophils, 6%; BUN, 50.7mg/dl; Cr, 7.6mg/dl; CRP, 34.0mg/dl. All drugs were discontinued because we suspected drug-induced acute renal failure, especially by cimetidine. Renal biopsy performed on day 3 showed interstitial nephritis with lymphocyte infiltration which was composed mainly of T cell. T4/T8 ratio was determined to be 1. There was neither predominance of helper nor cytotoxic cells in T cell subpopulation. We reviewed 22 cases reported and discussed the features of cimetidine-induced interstitial nephritis. The most important thing is to monitor renal function periodically with the suspicion of this disorder. On the detection of abnormality of laboratory data, cimetidine should be discontinued.