The 1988 National Maternal and Infant Health Survey was conducted by the National Center for Health Statistics to study factors related to poor pregnancy outcome, such as adequacy of prenatal care; inadequate and excessive weight gain during pregnancy; maternal smoking, drinking, and drug use; and pregnancy and delivery complications. The survey is a nationally representative sample of 11,000 women who had live births, 4000 who had late fetal deaths, and 6000 who had infant deaths in 1988. Mothers were mailed questionnaires based on information from certificates of live birth, reports of fetal death, and certificates of infant death. Information supplied by the mother, prenatal care providers, and hospitals of delivery was linked with the vital records to expand knowledge of maternal and infant health in the United States. Data collection from the Longitudinal Followup of mothers in the survey began in January 1991. It provides information on health and development of low- and very low-birthweight babies, child care and safety, maternal health, maternal depression, and plans for adoption and foster care. Both surveys will provide useful data for clinicians in maternal and child health.