This report describes a 59-year-old woman, who, after an initial reaction to hydralazine, inadvertently took the drug again. She promptly developed symptoms of acute cholangitis--fever, right upper quadrant tenderness, obtundation, and hypotension. Cholecystectomy was performed and no obstruction or infection of the biliary tract was present. Perioperative studies support a diagnosis of hydralazine-induced acute cholangitis, a side effect of the drug which has not been previously described.