In recent decades mortality rates have declined for both white and nonwhite Americans, but national averages obscure the extremely high mortality rates in many inner-city communities. Using data from the 1980 census and from death certificates in 1979, 1980, and 1981, we examined mortality rates in New York City's Central Harlem health district, where 96 percent of the inhabitants are black and 41 percent live below the poverty line. For Harlem, the age-adjusted rate of mortality from all causes was the highest in New York City, more than double that of U.S. whites and 50 percent higher than that of U.S. blacks. Almost all the excess mortality was among those less than 65 years old. With rates for the white population as the basis for comparison, the standardized (adjusted for age) mortality ratios (SMRs) for deaths under the age of 65 in Harlem were 2.91 for male residents and 2.70 for female residents. The highest ratios were for women 25 to 34 years old (SMR, 6.13) and men 35 to 44 years old (SMR, 5.98). The chief causes of this excess mortality were cardiovascular disease (23.5 percent of the excess deaths; SMR, 2.23), cirrhosis (17.9 percent; SMR, 10.5), homicide (14.9 percent; SMR, 14.2), and neoplasms (12.6 percent; SMR, 1.77). Survival analysis showed that black men in Harlem were less likely to reach the age of 65 than men in Bangladesh. Of the 353 health areas in New York, 54 (with a total population of 650,000) had mortality rates for persons under 65 years old that were at lest twice the expected rate. All but one of these areas of high mortality were predominantly black or Hispanic. We conclude that Harlem and probably other inner-city areas with largely black populations have extremely high mortality rates that justify special consideration analogous to that given to natural-disaster areas.