Despite declines over the last decade in perinatal mortality in Blacks in the United States, the percentage of Black mothers who deliver low birth weight infants (less than 2500 grams) has remained almost unchanged at a rate about twice that of Whites. Although some suggest that the high percentage of low birth weight Black infants is genetic, the possibility that as yet unidentified personal and social factors in Blacks accounts for the high percentage of low birth weight infants has not been examined adequately. We here propose a case-control study in which we will seek to identify personal and social factors associated with low birth weight in Blacks. To do this, we will use birth registration information to identify as cases 400 low birth weight (750-2499 grams) singleton, Black infants without known congenital anomalies born in Alameda County in a 15 month period. These cases comprise all low birth weight, singleton Black infants without a known congenital anomaly born in Alameda County in the period chosen. Cases will be divided into those that are pre-term low birth weight and those that are intrauterine growth retarded. For each case group, a comparison group of equal size will be selected randomly from singleton, Black infants of birthweight 3000-4000 grams without known congenital anomalies, frequency matching to achieve an age and parity distribution similar to that in the cases. The mothers of the cases and the comparison groups will be interviewed in their homes. Information will be solicited on socioeconomic status, social environment, and certain qualitative aspects of dietary behavior prior to the pregnancy. The analysis will seek to identify factors associated with pre-term low birth weight and intrauterine growth retardation separately, testing six specific hypotheses about low birth weight.