The mortality in 1014 patients with ulcerative proctocolitis diagnosed while resident in Leicestershire identified in a population-based study from 1972 to 1989 was assessed. Ninety-two Europeans and one South Asian died. The standardized mortality ratio (SMR) in South Asians was 26 (95% confidence interval 0-147). In Europeans the overall mortality was not increased, the SMR was 93 (95% confidence interval 75-114). The SMR did not differ between established disease extents, but was highest in those patients in whom the extent was undefined (SMR = 237, 95% confidence interval 130-397). Comparison of SMRs and survival curves showed no difference in mortality in patients diagnosed from 1972 to 1980 and from 1981 to 1989. Mortality was similar in patients who had colectomy and those who had not (SMR = 130, 95% confidence interval 71-219, chi 2(1) = 1.2, NS). Mortality did not change during the study. These findings should be made available to patients and their families.