Relatively little is known or understood about the nature of complications that occur during a surgical procedure. Definitions, classification, and documentation are substantive challenges to comprehensive event capture. We hypothesized that our prospective complication database (ie, Surgical Activity Tracking System) would supplement traditional sources of intraoperative complication reporting.Consecutive patients undergoing surgery on a single general surgical service from June 2005 through May 2010 were selected for analysis. All cases had been entered into the Surgical Activity Tracking System, a prospective complication database that identifies and captures complications in real time, using a specially trained nurse practitioner. Intraoperative complications were grouped into 1 of 9 categories. Operative reports and discharge summaries were analyzed by an independent reviewer to determine if the complication(s) had been documented by a traditional data source.Eight thousand eight hundred and ninety-six operations were performed on 7,729 patients during the study period. One hundred and thirty-seven patients (1.5%) experienced an intraoperative complication. Nonintestinal organ lacerations, inadvertent enterotomies, and hemorrhage were the most common adverse events. The operative reports failed to mention 20 of the 151 complications (13%), and discharge summaries failed to report 22 complications (14%). Some complications, such as inadvertent enterotomy, were almost always reported, but others such as arrhythmia, were only occasionally described (25%).Our prospective complication tracking system identified a considerable number of complications that were not available in either the operative report or discharge summary. The number of unreported adverse events varied greatly by category, suggesting opportunities for improvement in both complication identification and tracking.