Allergic reactions are often unpredictable, sudden in onset and may be potentially lethal. Clinical manifestations are confined to skin (rash, urticaria, angioedema), respiratory tract (laryngeal edema, bronchospasm) and cardiovascular system (hypotension, bradycardia, dysrhythymia). Because cardiovascular collapse is the most common life-threatening clinical feature, immediate and proper treatment is necessary. We have experienced two cases of intraoperative anaphylatic shock between September 1988 and April 1989. The precipitating factors were of nonanesthetic origin (case 1 was probably due to cephalothin and case 2 was due to dextran 40). Both cases manifestated with hypotension, bradycardia, cutaneous rash and urticaria. Recovery was smooth and without sequela after volume expansion and sympathomimetic drug. We discuss these two cases with a brief review.