According to the 1980 census, blacks in Suffolk County on Long Island, NY, had a median family income of almost $20,000 versus $12,618 for blacks in the entire United States, or only 20 percent lower than that for whites in the county. Black-white ratios of age-specific death rates for 1979-83 in Suffolk County were elevated for all causes for men and women in age groups from 35-44 to 55-64 years (but not for those 75 years or older), for ischemic heart disease for women (but not men) for age groups from 35-44 to 55-64 years, for diabetes mellitus for most ages (especially for females), and for cerebrovascular disease for both men and women for all age groups from 35-44 to 65-74 years. The age-specific proportional mortality ratios (PMRs) for ischemic heart disease within educational level (less than 12 years and 12 or more years of school) were lower for black than for white men but more similar for black and white women. For diabetes, the PMRs were higher for black versus white women within both educational levels. PMRs for cerebrovascular disease were higher for black than white men within the group of decedents with less than 12 years of education. The findings are discussed with reference to racial differences in the prevalence of poverty as well as possible differences in risk factors (for example, obesity) or medical care independent of poverty.