During the initial assessment of trauma patients they usually undergo a Focused Assessment with Sonography for Trauma (FAST) in which there are occasionally incidental findings of other surgical conditions. In this audit we discuss the incidence, demographics, and implications of these findings and we propose a management algorithm. Within 2 years we managed 6041 trauma patients in the emergency department based on the Advanced Trauma Life Support protocols, 95 per cent of which underwent a FAST ultrasound. Incidental findings were reported in 468 patients (7.8%), whereas in a further 11.2 per cent of these patients there was a second finding. The mean age of these patients was 57.55 years (15-105), and most of them were men (51.1%). The vast majority of the findings were related to the liver and biliary tree (52.1%) followed by the urinary track (27.1% + 8%). In multivariate analysis only the age was a significant factor associated with incidental findings (P < 0.001) whereas in univariate analysis both the gender [men (54.1%) vs women (45.9), P = 0.013] and the mechanism of trauma (P < 0.001) were as important as the age (P < 0.001). The patients who had incidental findings were 15 years older than the rest. The detection of unknown surgical conditions in FAST may lead to managerial and possible medico-legal issues rendering the development of a proper algorithm mandatory.