Exposure to alcohol during gestation can cause persistent abnormalities in physical and cognitive development. Children who meet the clinical definition of fetal alcohol syndrome (FAS) are small for their age, exhibit characteristic facial anomalies, and demonstrate deficits in central nervous system development. Alcohol effects in children with prenatal exposure, but not FAS, are similar, although of smaller magnitude and not necessarily present in all three systems. The degree to which a person is affected by prenatal alcohol exposure depends on the amount, timing, and duration of the mother's alcohol consumption during pregnancy as well as maternal characteristics (e.g., age and comorbid psychiatric disorders) and environmental factors (e.g., socioeconomic status and family problems). Some exposure-related effects, such as growth deficits, are directly related to the amount of alcohol consumed, however, so that even a small amount of alcohol may affect child development. Therefore, the best policy continues to be abstinence during pregnancy.