Surgical site infections (SSI) are a costly problem. The purpose of this study was to determine the rate of infection and identify patient and technical risk factors for SSI in an orthopaedic ambulatory surgical center. Over 11,000 consecutive orthopaedic surgeries over 5 years were reviewed for SSI as well as demographic, medical, and surgical risk factors. Nearly 400 noninfected patients served as statistical controls. The overall infection rate was 0.33%, which compares favorably to previous studies of outpatient surgery and appears to be substantially lower than SSI rates previously reported for inpatient orthopaedic surgery. Male sex, smoking, and diabetes demonstrated significantly higher risk for infection. Surgery time and duration of anesthesia administration were also associated statistically with SSI. A history of cancer, hypertension, or thyroid problems were all associated with higher but statistically insignificant risk of SSI. Patient age and number of past surgeries were equal in the SSI and control groups.