HC growth retardation has been shown to be associated with opiate and polydrug exposure in newborns. Previous studies have also found modest correlations between HC and intelligence, with decreased HC at birth linked to lower cognitive functioning later in the life span. The current study examined the association between HC at birth/HC growth change and cognitive functioning at 36 months of age among a sample of 94 newborn infants born to cocaine and/or opiate using mothers. A comparison sample of non-exposed children was recruited from the same community. Data were collected via interview with mother, maternal toxicology screens, and child follow-up at 3, 6, 12, 18, 24, 30, and 36 months where weight, length, HC, and a health and social history were obtained. The Stanford-Binet Intelligence Scale and the Bayley Scales of Infant Development were administered to child participants at 36 months of age. Results of statistical analyses indicated that while the IUDE infants had smaller HC at birth, by 36 months of age the HC of the experimental and comparison groups were roughly equivalent. Moreover, no difference between groups was observed in the intelligence scores of the infants at 36 months. Future studies should focus on the subtle effects of prenatal drug exposure, including factors such as attention span and impulse control. Figures, tables, references