AIM: To determine the prevalence of ulcerative colitis (UC) in Malaysian patients and to establish the spectrum of the disease seen in Malaysian patients.METHODS: Data were obtained retrospectively from a review of the medical records of in- and out-patients with a diagnosis of UC at the University Hospital, Kuala Lumpur between 1985 and 1998.RESULTS: There were 45 confirmed cases of UC, of which 3 were foreigners, who were excluded from analysis.Thirty new cases of UC were diagnosed during the study period. Their mean age at presentation was 33.0±10.0 years.The highest prevalence of UC was 17.9/100 000 hospital admissions in the Indians, followed by 11.2/100 000 hospital admissions in the Chinese. The lowest prevalence was 3.7/100 000 hospital admissions in the Malays. The prevalence of UC was significantly higher in the Indians and the Chinese when compared with the Malays with an OR of 4.89 (CI = 2.02-12.24; χ2 = 15.45, P＜0.001) and 3.06 (CI = 1.24-7.78; χ2 = 6.30; P= 0.012) respectively. The extent of colonic disease was similar in the Malay and Indian patients. In contrast, distal or left-sided colitis predominated in the Chinese with an OR of 8.17 (95%CI = 1.31-64.87;χ2 = 5.53, P = 0.02). Extraintestinal manifestations were uncommon (11.9%).CONCLUSION: UC is an uncommon disease in Malaysia,but racial differences exist. The Indians had the highest prevalence of UC with the Chinese demonstrating the least extensive disease.