As the etiology of inflammatory bowel disease remains unknown, studies of its time trends may provide clues to understanding the underlying mechanisms. This study examines mortality from Crohn's disease and ulcerative colitis in England and Wales and the U.S. during the period 1950 to 1983. Mortality from Crohn's disease and ulcerative colitis changed in both countries similarly. The death rates from Crohn's disease increased until 1970 to 1974 and decreased thereafter. The death rates from ulcerative colitis decreased throughout the observation period. Similar time trends occurred in men and women, and in the U.S. in whites and nonwhites. In the U.S., the death rates from both diseases were twofold higher in whites than nonwhites. The temporal changes suggest that mortality from inflammatory bowel disease is affected by exogenous factors and that these factors are different for Crohn's disease than for ulcerative colitis. These factors seem to have changed similarly in England and in the U.S.