New York City trends in maternal drug abuse during pregnancy and in mortality rates for infants with in utero drug exposure are reported; causes of death among drug-exposed infants are studied, as is the association between maternal drug abuse and other factors that contribute to infant mortality (e.g., low birthweight, lack of prenatal care). Data for this study are derived from the linked files of New York City birth and infant death certificates. Reports of infants born to drug abusing mothers increased from 6.7 per 1000 live births in 1981 to 20.3 per 1000 live births in 1987, with abuse of cocaine accounting for most of the rise. When standardized for race and ethnicity, the mortality rate for drug-exposed infants born from 1978 through 1986 was 35.9, or 2.4 times that for infants in Ncw York City in general. Drug-exposed infants were over three times as likely as infants in the general population to be of low birthweight. The association of both opiates and cocaine with increased mortality and low birthweight was similar. Death rates from SlDS and AIDS were especially higher for drug-exposed infants than for those in the general population, and were similar for opiate- and cocaine-exposed infants. The impact of drug abuse on infant mortality rates in selected low socioeconomic health districts is discussed.