Patients with coagulation disorders present the entire open-heart surgical team with an increased challenge. A patient with a known history of moderately severe Factor IX deficiency (2.4% activity) was evaluated for coronary artery disease. Cardiac catheterization revealed a 99% right coronary artery lesion, a long 99% circumflex lesion and normal left ventricular function. Sextuple coronary artery bypass grafting was performed with the aid of aprotinin and Factor IX transfusions. The patient's platelet count after cardiopulmonary bypass was 65,000/mm3, down from a preoperative level of 172,000/mm3, requiring the transfusion of six units of pooled platelets immediately postoperation. The patient was extubated five and a half hours after arriving in the Intensive Care Unit, and his chest-tube drainage after the first 24 hours was 373 ml. Other than a transient episode of atrial fibrillation on the third postoperative day, the patient had an uneventful postoperative course and was discharged on the sixth postoperative day. With the use of aproptinin and the newer monoclonal antibody-purified Factor IX concentrates that have been developed, many of the added risks of performing open-heart surgery on patients with haemophilia B are greatly reduced if not eliminated.