Procedural checklists may be useful for increasing the reliability of safety-critical processes because of their potential capacity to improve teamwork, situation awareness, and error catching. To test the hypothesized utility and adaptability of checklists to surgical teams, we performed a randomized controlled trial of procedural checklists to determine their capacity to increase the frequency of safety-critical behaviors during 47 laparoscopic cholecystectomies. Ten attending surgeons at an academic tertiary care center were randomized into two equal groups - half of these surgeons received basic team training and used a preprocedural checklist whereas the other half performed standard laparoscopic cholecystectomies. All procedures were videotaped and scored by trained reviewers for the presence of safety-critical behaviors. There were no differences detected in patient outcomes, case times, or technical proficiency between groups. Cases performed by surgeons in the intervention (checklist) group were significantly more likely to involve positive safety-related team behaviors such as case presentations, explicit discussions of roles and responsibilities, contingency planning, equipment checks, and postcase debriefings. Overall, situational awareness did not significantly differ between the intervention and control groups. Participants in the intervention (checklist) group consistently rated their cases as involving less satisfactory subjective levels of comfort, team efficiency, and communication compared with those performed by surgeons in the control group. Surgical procedural safety checklists have the capacity to increase the frequency of positive team behaviors in the operating room during laparoscopic surgery. Adapting to the use of a procedural checklist may be initially uncomfortable for participants.