Purpose: The need to improve efficiency in endoscopy units is receiving attention because of increased demand for screening colonoscopy. One solution is to increase the volume of endosocpic services available by efficiently utilizing existing resources. The purpose of this study was to assess efficiency in the endoscopy unit of a large tertiary care teaching hospital. Methods: A research assistant collected data prospectively over 3 months in the endoscopy unit of a 650 bed acute-care teaching hospital. The data collected on inpatient and outpatient procedures included time intervals between endoscopic procedures and procedure durations. Procedure delays (defined as time interval between procedures of >15 minutes) were determined and the reasons for them recorded. For inpatients, the number of additional days spent waiting in hosptial for endoscopic procedures was also recorded. Results: From May 16-September 5, 2003, 675 endoscopic procedures were observed in 625 patients of whom 207 (33%) were inpatients. The most common procedure performed was colonoscopy (42.1%) followed by esophagogastroduodenoscopy (36%). Overall, in 193/625 patients (30.9%), the procedures were delayed (>15 minutes between procedures). Of these, the time interval between procedures was >30 minutes in 24.4%. The delays were physician-related in 54.4% (physician was not available to start the procedure). Procedure duration was prolonged in 22% of procedures. 86/207 (41.5%) inpatients waited at least one day in hospital for their procedures. Conclusions: Procedure delays were considerable and physician unavailability contributed to these delays. Strategies to reduce procedure delays could have a favorable impact on the volume of procedures performed in the unit, thereby improving utilization of existing resources. The generalizability of these findings is not known although it is widely perceived that the delivery of endoscopic services in large tertiary care teaching hospitals may not be as efficient as in other settings. Our results support this observation. We encourage other groups to assess the efficiency in their endoscopy units.