Among 22 cases of drug-induced acute interstitial nephritis (AIN), noncaseating interstitial granulomas were found in eight cases (36%). Acute renal failure (ARF), oliguric in three patients, appeared within 1-20 days after the beginning of therapy. Clinical symptoms suggesting a hypersensitivity reaction were unusual, marked blood eosinophilia was absent, and immunologic tests were inconstantly positive. The discovery of interstitial granulomas may be a clue to the diagnosis of drug-induced AIN, especially when the inflammatory infiltrates do not contain eosinophils. Since significant residual renal impairment may be observed the benefit of early steroid therapy must be debated.