Transfusion complications include ABO/Rh incompatibility, sepsis, febrile reaction, immunosuppression, and viral transmission. We experienced a case of anaphylactic reaction in a 40-year-old male scheduled for laminectomy. Anesthesia was induced by intravenous (I.V.) thiopental sodium and maintained with enflurane / N2O / oxygen. Vital signs were stable until 2 hours into surgery, when patient developed sudden profound hypotension (systolic pressure 60 mmHg) with tachycardia, skin flushing and bronchial wheezing shortly after infusion of only a few milliliters of 4th unit of whole blood. Blood transfusion was immediately stopped, anesthetic agents were discontinued, and 100% oxygen was administered. Rapid administration of I.V. fluids was begun and I.V. hydrocortisone along with pheniramine were administered. Patient was successfully treated and eventually discharged from the hospital. In conclusion, besides hemolytic transfusion reaction, anaphylactic transfusion reaction may cause severe hypotension. One should be aware of the potential for adverse effects including anaphylaxis, should recognize them immediately and treat them appropriately.