The authors report the cases of 3 patients who died from fulminant hepatitis after receiving iproclozide, a hydrazine-containing monoamine oxidase inhibitor. Fulminant hepatitis in these patients resembled that reported in patients receiving other hydrazine-containing monoamine oxidase inhibitors: (1) the 3 patients were women; (2) the monoamine oxidase inhibitor has been ingested for 1 month or more; (3) the main clinical manifestations were jaundice and disorders of consciousness; (4) hypersensitivity manifestations were absent; (5) the predominant liver lesion was necrosis; (6) all 3 patients died. In our 3 patients, jaundice occurred 7 to 10 days after the adjunction to iproclozide of a microsomal enzyme inducer. These observations suggest that concomitant administration of iproclozide and of microsomal enzyme inducers may produce fulminant hepatitis in man. It is speculated that iproclozide could be, like iproniazid, transformed into a hepatotoxic metabolite, the production of which would be increased by microsomal enzyme induction.