Prospective data from a population of newborn infants were searched for risk factors for Sudden Infant Death Syndrome (SIDS). Maternal smoking, younger maternal age, short intervals between pregnancies, gestational age of less than 40 weeks, birth weight of less than 3000 g, lower socioeconomic status and male sex were factors found to be associated with SIDS. Race, blood type, maternal hemoglobin level, placental abnormality and newborn condition were not associated with SIDS in this population. Scoring systems to predict which infants will die of SIDS are not yet sensitive enough for clinical use.