Background: The risk for colorectal cancer (CRC) in ulcerative colitis (UC) in India is not known. Method: Retrospective cohort from a tertiary level hospital in South India. Analysis of archived records of all patients with UC who underwent colonoscopy and segmental biopsies over the last 25 years. Incidence densities and risk of developing high grade dysplasia or CRC was calculated and chi-squared test was performed for risk factors of interest. Results: Complete records were available for 532 patients, 336 (63.2%) male. The mean (± SEM) duration of illness was 6.04 ± 0.29 years. In total, 234 patients (44%) had pancolitis, 121 (22.7%) had left-sided colitis and 177 (33.3%) had proctitis or proctosigmoiditis. Overall, five (0.94%) patients developed carcinoma and one (0.19%) patient had high grade dysplasia. The incidence density and risk of developing either CRC or high grade dysplasia was zero in the first 10 years of disease. In those with disease duration of 10-20 years, incidence density was 2.34 per 1000 person years' duration (PYD) for all patients with colitis and 4.5 per 1000 PYD for patients with pancolitis alone. This corresponded to risks of 2.3% and 4.4%, respectively. For those with disease duration longer than 20 years, incidence density was 2.73 per 1000 PYD for all patients and 4.9 per 1000 PYD for patients with pancolitis. This corresponded to risks of 5.8% and 10.2%, respectively. Duration of disease beyond 10 years and extent of colitis were the only risk factors significantly associated with CRC. Conclusions: The risk of developing CRC is Indian patients with UC is lower than that reported from the West. Strategies for cancer surveillance in Indian patients with UC need to be tailored accordingly. © 2005 Blackwell Publishing Asia Pty Ltd.