OBJECTIVE: This study examined the cross-sectional association between platelet membrane serotonin 2A (5-HT2A) receptor variables in children and characteristics of their parents that place these children at risk for antisocial behavior. METHOD: As part of a larger prospective study investigating predictors of antisocial behavior, 38 younger brothers of convicted delinquents provided platelet samples; samples from 34 boys (mean age=8.3 years) were usable. The authors determined the density (Bmax) and affinity (Kd) of platelet membrane 5-HT2A receptors by using [3H]lysergic acid diethylamide. They also measured parental characteristics related to serotonergic dysfunction in prior studies, the quality of parent-child interactions, and psychiatric profiles of the boys who provided platelets. RESULTS: Bmax was significantly lower in boys whose parents had histories of substance abuse or incarceration. Bmax was also inversely related to harsh parenting; boys raised in environments characterized by frequent parental physical punishment and anger had a significantly lower Bmax. Bmax was not related to boys' disruptive behavior. CONCLUSIONS: In boys at risk for antisocial behavior, the density of 5-HT2A receptors on platelets is inversely related to parental factors known to place youth at risk for antisocial behavior.Abstract Teaser