Despite a large body of evidence describing care processes known to reduce the incidence of surgical site infections, many are underutilized in practice. Fifty-six hospitals volunteered to redesign their systems as part of the National Surgical Infection Prevention Collaborative, a 1-year demonstration project sponsored by the Centers for Medicare & Medicaid Services. Each facility selected quality improvement objectives for a select group of surgical procedures and reported monthly clinical process measure data. Forty-four hospitals reported data on 35,543 surgical cases. Hospitals improved in measures related to appropriate antimicrobial agent selection, timing, and duration; normothermia; oxygenation; euglycemia; and appropriate hair removal. The infection rate decreased 27%, from 2.3% to 1.7% in the first versus last 3 months. The Collaborative demonstrated improvement in processes known to be associated with reduced risk of surgical site infections. Quality improvement organizations can be effective resources for quality improvement in the surgical arena.