The interest in ambulatory surgery has grown substantially during the past ten years. To evaluate the medical aspects of ambulatory care objectively, there must be accurate, reliable, and pertinent complication data. A prospective study of 13,433 patients at a freestanding ambulatory surgical center was performed. Ninety-nine and eight-tenths percent of the patients were followed up through the first two postoperative weeks. One hundred six medical, surgical, or anesthetic complications were identified in the patient population. No deaths occurred in the center, and there was no instance of cardiovascular collapse. Sixteen patients were transferred to a general hospital. Surgery and anesthesia performed in either the inpatient or outpatient setting may be associated with serious complications. Many surgical procedures can be performed as safely in the outpatient setting as in the hospital inpatient setting.