In an effort to learn more about resource utilization on ambulatory surgery in hospital departments of surgery and its impact on quality of care, we re viewed the causes of postoperative hospital retention following ambulatory surgery in a hospital-based program. Of 1971 patients operated on in a 6-month period, 188 were retained for a rate of 9.5%. Of these, 71 (3.6%) were retained for observation and 42 (2.1%) for surgery more extensive than planned. The remaining 75 (3.8%) patients represent complications of surgery or anesthesia. The age distribution of pa tients with complications was the same as the group overall with a single mode at about 30 years, while the distribution of patients retained for observation or who were admitted the day of surgery was bimodal with a second peak at about 70 years. All surgical specialties had comparable rates of postoperative re tention, except gynecology which was significantly lower. Many of the patients had multiple procedures or surgery more extensive than planned.
