Abstract Aims Determine human factors implicated in cases submitted to the Confidential Reporting System in Surgery (CORESS), using the non-technical skills for surgeons (NOTSS) framework. Methods Consecutive cases submitted to CORESS, between 2005 and 2011 were evaluated as an interim analysis. The type of case, whether patient harm occurred, Clavien-Dindo (CD) classification, and the location of the incident were collected. Demographic data was not collected because they are often changed to protect patient identification. Each case was reviewed according to the non-technical skills for surgeons (NOTSS) taxonomy. Results There were 100 cases included in this interim analysis. The most common types of cases were delayed diagnosis (n=19), known complications (n=10), near misses (n=10), poor surgical technique (n=9), misuse of equipment/device (n=8), and wrong site surgery (n=5). Two-thirds of patients were harmed, with complications ranging from minor to life-threatening (9 CD I, 10 CD II, 32 CD III, 12 CD IV), and 4 resulting in death (CD V). Incidents occurred most frequently in the operating theatre (n=54), the ward (n=16), or the emergency department (n=9). There were 71 incidents that endangered patient safety related to deficiencies in situational awareness, 59 to poor communication and teamwork, 48 to poor decision-making, and 48 related to leadership failures. Conclusions The main human factors implicated in surgical patient safety incidents related to errors in situational awareness, communication and teamwork, and to a lesser extent, decision-making, and leadership. Efforts to prevent medical errors should be focused on clinician human factors training.