Cholestatic jaundice associated with chills, pruritus and blood eosinophilia developed in a patient who received prajmalium bitartrate therapy for ventricular arrhythmia following acute myocardial infarction. Discontinuation of the drug resulted in a spontaneous improvement in the clinical and biochemical findings. Challenge by prajmalium bitartrate caused rapid reappearance of the clinical and biochemical features. In immunological studies, deposits of IgG and IgA were detected at the bile canaliculi by fluorescent staining, and the patient's lymphocytes produced macrophage migration inhibition after in vitro incubation with prajmalium bitartrate. Thus, laboratory results support the assumption of an allergic mechanism.