Communication failures are a well-characterized source of errors in the operating room. This study used direct observation of surgical procedures to assess the incidence, types, and consequences of surgical communication problems, and found that failure to discuss equipment problems and progress of the procedure were common, resulting in delays, inefficiency, and workarounds. Teamwork training and implementation of formalized checklists have successfully improved communication and clinical outcomes in surgical patients, and in this study, implementation of a teamwork training program was associated with fewer communication failures.