Typically, the rate of abusive drinking during pregnancy considerably exceeds the rates of fetal alcohol syndrome (FAS) and alcohol-related birth defects, suggesting that other factors may modify the impact of alcohol on the developing organism. Data in the literature supporting this susceptibility hypothesis are sparse. In this paper, two studies in different samples, using different analytic strategies to examine susceptibility to different adverse outcomes are presented. Among 176 pregnancies in which lowered birth weight for gestational age was detected as an effect attributable to frequent beer drinking, 27 infants weighted less than 2,700 grams and 149 weighed more. Using discriminant analysis to contrast these groups, lowered birth weight for gestational age was associated with black race and lower maternal weight and weight gain. The effects of these factors were additive with that of persistent alcohol exposure; no interactions were detected, but pregnancies with risks in addition to alcohol were more likely to yield growth-retarded infants. In a second study, pregnancies resulting in 25 FAS cases were contrasted with 50 controls. A four-factor model accounted for nearly two-thirds of the explainable variance in the occurrence of FAS. Adjusted for frequency of maternal drinking, chronic alcohol problems and parity, there was a sevenfold increase in risk for FAS among black infants. The findings from both studies are consistent with the susceptibility hypothesis and have potentially important implications for public health and clinical approaches to prevention, as well as for future research.