A number of drug administered during anesthesia can provoke pathologic response by immunologic or nonimmunologic mechanisms. Known drugs involved in hypersensitivity reactions are muscle relaxants, local anesthetics, narcotics, barbiturates, contrast media, protamine and antibiotics. Clinical manifestations of anaphylaxis are diverse, but during anesthesia, cardiovascular collapse is predominate. We experienced a case of anaphylactoid reaction with erythema on upper thoracic region, severe hypotension, tachycardia and ventricular fibrillation. After defibrillation, the patient was recovered. During follow-up, we knew that this patient was exposed aprotinin repeatedly, and suspect the possibility of anaphylactoid reaction due to aprotinin.