Between 1960 and 1979, three studies were conducted in the Baltimore Standard Metropolitan Statistical Area to ascertain the incidence rates of first hospitalizations for ulcerative colitis and Crohn's disease. The age-adjusted rates per 100,000 population for the 1977-1979 survey for ulcerative colitis in white and nonwhite males and females were 2.92, 1.79, 1.29, and 2.90, respectively; the Crohn's disease rates were 3.39, 3.54, 1.29, and 4.08, respectively. In Baltimore the age-adjusted rate for Crohn's disease has increased to exceed the ulcerative colitis rate for whites of both sexes and nonwhite females. The ulcerative colitis and Crohn's disease rates for nonwhite males are similar. The rate for white males exceeds that for nonwhite males for both ulcerative colitis and Crohn's disease, but the converse is true for females. Females have higher rates than males for Crohn's disease in both color groups and for ulcerative colitis among nonwhites. White ulcerative colitis rates are higher for males than for females. From the first to the second surveys, the white male and female rates for ulcerative colitis converge with increasing male and decreasing female rates, but then both decline from the second to the third surveys. For Crohn's disease, the age-adjusted rates increased for whites of both sexes and nonwhite females from the first to second surveys. The Crohn's disease rates appeared to stabilize for whites of both sexes between the second and present surveys, but they increased for nonwhites of both sexes. Trends in age-adjusted rates for other areas are also discussed.