Acute interstitial nephritis (AIN) has been reported in association with therapy with a number of drugs. We report a patient who developed drug-related AIN while receiving intravenous amoxicillin therapy. The patient developed rash, secondary temperature elevation, and eosinophilia in association with nonoliguric renal failure. Renal biopsy showed evidence for AIN and the renal failure was responsive to corticosteroid therapy. AIN may occur in patients receiving any drug of the penicillin class. This reversible form of acute renal failure must not be overlooked in patients with other forms of renal disease.