Background: Sleep deficiency can adversely affect the performance of resident physicians resulting in greater medical errors. However, the impact of sleep deficiency on surgical outcomes, particularly among attending surgeons is less clear. Methods: Sixty attending surgeons from academic and community departments of surgery or obstetrics and gynecology were studied prospectively using direct observation and self-report to explore the effect of sleep deprivation on patient safety, operating room communication, medical errors, and adverse events while operating under two conditions, Post-Call (defined as >2 hours of nighttime clinical duties) and Non-Post-Call. Results: Each surgeon contributed up to five surgical procedures post-call and non-post-call yielding 362 cases total (150 Post-Call and 210 Non-Post-Call). Most common were caesarian section and herniorrhaphy. Hours of sleep on the night before the operative procedure were significantly less Post-Call (4.98 ± 1.41) vs. Non-Post-Call (6.68 ± 0.88, p<0.01). Errors were infrequent and not related to hours of sleep or post-call status. However, Non-Technical Skills for Surgeons (NOTSS) ratings demonstrated poorer performance while Post-Call for Situational Awareness, Decision Making and Communication/Teamwork. Fewer hours of sleep also was related to lower ratings for Situational Awareness and Decision Making. Decreased self-reported alertness was observed to be associated with increased procedure time. Conclusions: Sleep deficiency in attending surgeons was not associated with greater errors during procedures performed during the next day. However, procedure time was increased suggesting that surgeons were able to compensate for sleep loss by working more slowly. Ratings on non-technical surgical skills were adversely affected by sleep deficiency.