All patients undergoing surgery in the institution's main operating suites between January 2, 1999, and February 2, 1999, were identified using the hospital's computerized database to determine potential eligibility. Surgery that took place outside this arena was limited to "day-stay" procedures. Patients who were 18 years and older and who underwent major noncardiac surgery were considered potentially eligible. Surgical procedures considered major for this study were determined by a group of physicians and nurses representing the departments of surgery, anesthesiology, and internal medicine. These procedures include the following: orthopedic procedures, including total knee/hip replacement, bipolar hip replacement, open reduction internal fixation (hip or pelvis), and limb amputation; vascular procedures, including aortofemoral bypass, abdominal aortic aneurysm repairs, and any other surgery on the aorta; intra-abdominal procedures, including colectomy, splenectomy, pancreatoduodenectomy (Whipple procedure), radical prostatotomy, radical hysterectomy, liver resection, nephrectomy, and total abdominal hysterectomy/bilateral salpingo-oophorectomy; and intrathoracic procedures, including all invasive noncardiac procedures. We excluded patients undergoing day-stay surgery and those who underwent a second surgical procedure during a single hospitalization. Demographic data, including age, sex, race, type of surgery, length of hospital stay, and prior use of β-blockers, were collected for all potentially eligible patients.