The adverse effects of fetal drug exposures are well documented. Evidence for FAS, impaired intrauterine growth, birth defects, and mental retardation related to alcohol is compelling; evidence for alcohol-induced adverse behaviors and impaired speech is tenuous. Teratogenic, cognitive, or behavioral effects associated with prenatal exposure to marijuana, cigarettes, cocaine, or opiates have not been well established. The most convincing finding related to prenatal exposure to such substances is IUGR. Impaired fetal growth, especially of brain, may indirectly mediate drug effects on cognition. The abnormal neonatal neuro-behaviors described herein have no apparent impact on subsequent development. The development of opiate-exposed children, particularly those with withdrawal symptoms, however, appears to be more vulnerable to the adverse effects of an impoverished environment.