We performed a population-based, case-control study of the risk of ulcerative colitis associated with coffee and alcohol use among the 304,000 members of a prepaid health plan. We compared coffee and alcohol use histories before ulcerative colitis onset in 209 cases and an equal number of age- and sex-matched controls selected from the enrollment file of the prepaid health plan. Neither coffee use, amount of coffee consumed daily, or cumulative coffee consumption before disease onset altered the risk of developing ulcerative colitis. A decreased risk of ulcerative colitis was associated with alcohol consumption before disease onset among never-smokers only. This risk declined as daily alcohol consumption increased. These results suggest that alcohol consumption may lower ulcerative colitis incidence.