Newark, a metropolitan industrial town, experienced the highest infant mortality of any major city in the United States in the 1960s and early 1970s. Between 1970 and 1973, however, infant mortality among non-whites in this city declined strikingly. This decline could not be directly related to declines (a) in birth rates, (b) in the proportions of babies of low birth weight, (c) in the proportions of babies born to mothers in unfavorable age groups, (d) in the general fertility rates, or (e) in the illegitimacy rates. The decline may have been related (a) to the removal from childbearing cohorts of the group of females in the population--as yet undefined--whose babies would have been at high risk of infant mortality, (b) to the falling birth rate, (d) to better postnatal care--or to all of these factors. The study data suggest a multifactorial basis for the precipitous decline and also suggest that further major reductions in infant mortality among both nonwhites and whites will require better definition of the causes of low birth weight.