Cancelled elective surgical cases result in wasted operating room time and additional hospital expense. We prospectively reviewed 1063 scheduled cases that resulted in 184 (17%) cancellations. For outpatient surgery, urology had significantly more, and orthopedic and pediatric surgery significantly fewer cancellations. For inpatient surgery, plastic surgery had significantly more and orthopedic surgery and obstetrics and gynecology significantly fewer cancellations. Lack of medical clearance and outpatient "no shows" accounted for the majority of avoidable cancellations. Case cancellations can be decreased by improved preoperative patient evaluation, improved communication between physician and patient, and modified schedule design.