Genetic and environmental influences on self-reported parent-child relationships were examined in a sample of 824 individual male twins and their parents. Cross-sectional comparisons of twin similarity at ages 11 and 17 were undertaken to identify developmental changes in the contribution of genetic and environmental factors to family relationships. Significant genetic influences were found on perceptions of parent-son conflict, regard, involvement, and overall support. Heritabilities were significantly higher in older twins, suggesting increased genetic influence with age. Age differences were present primarily in the father-son relationship. These results provide support for the proposal of S. Scarr and K. McCartney (1983) that the importance of active gene-environment correlations increases during adolescence. Older adolescents may have more choice and impact on the nature of the relationships they have with their parents.