The thiopurine (TP) analogs azathioprine and mercaptopurine have proven efficacy in inducing and maintaining clinical remission in Crohn's disease (CD). Their impact on the long-term need for surgery is uncertain since studies have reported conflicting results. The aim of this systematic review was to summarize and evaluate evidence of the published literature regarding those studies assessing the impact of TPs on the risk of first surgical resection in CD.