Children with fetal alcohol spectrum disorders (FASD) show behavioral and intellectual impairments that indicate frontal lobe dysfunction, but the extent of damage to this region has not been clarified by brain imaging studies. This study uses the St Kitts vervet monkey, a species that voluntarily consumes beverage alcohol, to examine the effects of prenatal ethanol exposure. Pregnant vervets were allowed to drink the equivalent of 3-5 standard drinks four times a week during the third trimester. Using unbiased stereology, we estimated neuronal reduction and found significantly fewer cells in the frontal lobes of FASD offspring as well as an increased density of interstitial white matter neurons. These cytoarchitectonic effects are consistent with the behavioral and cognitive changes observed in FASD.