Genetic and environmental influences in social attitudes were investigated in adopted and nonadopted children (N = 654) and their biological and adoptive relatives in the Colorado Adoption Project. Conservatism and religious attitudes were measured in the children annually from ages 12 to 15 and in the parents during the 12-year-old visit. Multivariate genetic model fitting indicated that both conservatism and religious attitudes are strongly influenced by shared-family environmental factors throughout adolescence. In contrast to previous findings from twin studies, which suggest that genetic influence on social attitudes does not emerge until adulthood, the present study detected significant genetic influence in conservatism as early as age 12. There was no evidence of genetic influence, however, on religious attitudes during adolescence.