Although gene × environment studies are typically based on the assumption that some individuals possess genetic variants that enhance their vulnerability to environmental adversity, the differential susceptibility model posits that these individuals are simply more sensitive to social context, whether that context be adverse or supportive. Thus, those persons most vulnerable to adversity are the same ones who reap the most benefit from support. This idea was tested using longitudinal data from a sample of several hundred African Americans. The findings indicated that relatively common variants of the GABRA2 gene interact with parenting to predict hostility toward romantic partners in a manner consonant with the differential susceptibility hypothesis. Individuals with these genetic variants displayed more aggression toward their partner than those with other genotypes when they had been subjected to harsh parenting, but they exhibited less aggression toward their partner than other genotypes if their parents had avoided harsh parenting practices.