As part of the UCLA Family Lifestyles Project (FLS), 200 male and female children participated in an 18-year longitudinal outcome study of early childhood exposure to parental nudity and scenes of parental sexuality ("primal scenes"). At age 17-18, participants were assessed for levels of self-acceptance; relations with peers, parents, and other adults; antisocial and criminal behavior; substance use; suicidal ideation; quality of sexual relationships; and problems associated with sexual relations. No harmful "main effect" correlates of the predictor variables were found. A significant crossover Sex of Participant X Primal Scenes interaction was found such that boys exposed to primal scenes before age 6 had reduced risk of STD transmission or having impregnated someone in adolescence. In contrast, girls exposed to primal scenes before age 6 had increased risk of STD transmission or having become pregnant. A number of main effect trends in the data (nonsignificant at p < 0.05, following the Bonferonni correction) linked exposure to nudity and exposure to primal scenes with beneficial outcomes. However, a number of these findings were mediated by sex of participant interactions showing that the effects were attenuated or absent for girls. All effects were independent of family stability, pathology, or child-rearing ideology; sex of participant; SES; and beliefs and attitudes toward sexuality. Limitations of the data and of long-term regression studies in general are discussed, and the sex of participant interactions are interpreted speculatively. It is suggested that pervasive beliefs in the harmfulness of the predictor variables are exaggerated.