Dr. I was vaguely disturbed by something about the slim, handsome young man who was in his examining room because of an unstable knee. The knee, however, had unequivocal indications for surgical repair of three ligaments. It could probably be done by arthroscopy but might require an open procedure. The patient agreed to the procedure and it was scheduled. Dr. I asked him to provide a blood sample for routine laboratory tests. He also scheduled a preoperative chest X-ray. After the patient left, Dr. I added an HIV test to the laboratory request. Dr. I was anxious about blood-borne infections and was glad he had gotten his hepatitis B shots. He knew one colleague who had been very ill from that viral infection and another one who was a hepatitis B antigen carrier but had been afraid to reveal that at his hospital or clinic for fear of losing his privileges. The day before the planned surgery, the patient's laboratory and radiology reports came back. His blood cell count showed reduced lymphocytes. His clotting studies were normal. The HIV test was positive. To make matters even more perplexing, the radiologist reported a lung infiltrate that suggested tuberculosis. Dr. I wondered about what to tell his patient and what to do about the surgery.