Purpose: There is a risk of developing a trocar site hernia (TSH) after laparoscopic surgery, but data is sparse and based mostly on retrospective studies with a short and poorly defined follow-up period. Surgical approaches and patient-related co-morbidity have also been suggested as risk factors for development of TSH. The aim of the present review was to perform a qualitative systematic analysis to estimate the incidence of TSH and to discuss the surgical and patient-related risk factors for development of TSH. Methods: The literature search was until 19 May 2010. Studies with TSH, defined as either operation for TSH or a hernia found during clinical follow-up, were included. We included randomised controlled trials, prospective non-controlled studies including >200 patients, and retrospective studies including >200 patients. The review was completed according to the PRISMA guidelines. Results: We included 19 studies in adults and 3 studies in paediatric patients (<18 years), and a total of 30,568 adults and 1,098 children were analysed. The overall incidence of TSH was 0-5.2%. TSH occurred most often (96%) in trocar sites of a minimum of 10 mm, located mostly in the umbilicus region (82%). Data supported a higher incidence of TSH when the trocar site fascia was not sutured, and in pre-school children undergoing a laparoscopic procedure. Conclusions: Current data suggests a relatively low incidence of TSH but that all trocar incisions of a minimum of 10 mm should be closed. In pre-school children undergoing laparoscopic surgery, all port sites should be closed.