Knowing when judgment errors are more likely to occur can increase surgeons' awareness before, during, and after procedures. This study examined the records of 131 patients with 30-day morbidity or mortality to identify any errors in judgment that may have contributed to harm. Examples of errors in judgment included inappropriate operation, premature discharge, and premature removal of drain. Most errors occurred post-operatively (including after discharge) and in colorectal and hepatobiliary procedures.