Introduction The American College of Surgeons guidelines indicate that skull caps are acceptable, while the Association of periOperative Registered Nurses recommend bouffant caps. However, no scientific evidence has shown a significant advantage in surgical site infection (SSI) reduction with either cap. The objective of this study was to determine the influence of surgical cap choice on SSIs. Methods Data from a previously published prospective randomized trial on the impact of hair clipping on SSI rates were analyzed. Patients were grouped by the attending surgeons' preferred cap choice into either bouffant or skull cap groups. Results Overall, 1543 patients were included in the trial. Attending surgeons wore bouffant caps (39%) and skull caps (61%) of cases. Prevalence of diabetes and tobacco use were similar between the groups. Bouffant caps were used in 71% of colon/intestine, 42% of hernia/other, 40% of biliary cases and only 1% of foregut cases. Overall, SSIs occurred in 8% and 5% of cases with a bouffant and skull cap, respectively (p=0.016), with 6% vs 4% classified as superficial (p=0.041), 0.8% vs 0.2% deep (p=0.120), and 1% vs 0.9% organ space (p=0.790); however, when adjusting for the type of surgery, no significant differences in SSI rates were observed between bouffant versus skull caps. Conclusions Surgeon preference for bouffant versus skull caps do not significantly impact SSI rates after accounting for surgical procedure type. Surgeon preference should dictate choice of head wear in the operating room. Source