With the use of behavioral genetics methodology, in which variance of an observed trait can be decomposed into the effect of three latent variables, that is, genetic, shared environmental, and nonshared environmental, factors contributing to the formation of authoritarian conservatism were examined. 4111 participants (1279 male twins and 1899 female twins between the ages of 12-26, as well as 83 fathers and 860 mothers of the twins) responded to the Authoritarian Conservatism Scale. The twin model analysis employing 912 pairs of identical and 630 pairs of fraternal twins accounted for 33% of the variance of authoritarian conservatism by genetics, and 67% by nonshared environment. The subsequent twin parent-offspring model analysis also produced a very similar result. Thus, it was revealed that what mediated the familial transmission of authoritarian conservatism was genetics, not cultural transmission. Theories explaining the formation of authoritarianism by parenting or social background of the family are not supported. Transmission models can be further elaborated by including genetics as a predictable variable.