BACKGROUND: The intestinal microflora is thought to be the origin for many infectious complications seen in surgical conditions, due to dysfunction of the intestinal barrier and bacterial translocation. Probiotics may produce beneficial effects on the intestinal barrier function and help reduce the incidence of infectious complications in this group of patients. METHODS: Medical databases were searched for randomised controlled studies regarding the use of probiotics or synbiotics in surgical patients. RESULTS: There was no significant benefit in the use of synbiotics in elective abdominal surgery. Patients undergoing hepatopancreatobiliary surgery or liver transplantation showed significant reductions in post-operative infectious complications, as did trauma patients. Despite promising early studies, the most comprehensive study involving acute pancreatitis showed an increased mortality. CONCLUSIONS: Probiotics or synbiotics may protect against post-operative infectious complications in certain surgical conditions, but caution must be exercised. Use in acute pancreatitis should be avoided at the present time.