BACKGROUND: Colonoscopic surveillance provides the best practical means for preventing colorectal cancer (CRC) in inflammatory bowel disease (IBD) patients. Strong evidence for improved survival from surveillance programmes is sparse. METHOD: The aim of this study was to compare tumour stage and survival of IBD patients with CRC who were a part of a surveillance programme with those who were not. A nationwide pathology database (PALGA (pathologisch anatomisch landelijk geautomatiseerd archief)) was consulted to identify IBD patients with CRC treated in all eight university hospitals in The Netherlands over a period of 15 years. Patients were assigned to the surveillance group when they had undergone one or more surveillance colonoscopies before a diagnosis of CRC. Patients who had not undergone surveillance served as controls. Tumour stage and survival were compared between the two groups. RESULTS: A total of 149 patients with IBD-associated CRC were identified. Twenty-three had had colonoscopic surveillance before CRC was discovered. The 5-year CRC-related survival rate of patients in the surveillance group was 100% compared with 74% in the non-surveillance group (P = 0.042). In the surveillance group, only one patient died as a consequence of CRC compared with 29 patients in the control group (P = 0.047). In addition, more early tumour stages were found in the surveillance group (P = 0.004). CONCLUSIONS: These results provide evidence for improved survival from colonoscopic surveillance in IBD patients by detecting CRC at a more favourable tumour stage. British Journal of Cancer (2009) 101, 1671-1675. doi:10.1038/sj.bjc.6605359 www.bjcancer.com Published online 13 October 2009 (C) 2009 Cancer Research UK