This article takes issue with the behavior-genetic analysis of parenting style presented by M. McGue, I. Elkins, B. Walden, and W. G. Iacono. The author argues that the attribution of their findings to inherited genetic effects was without basis because McGue et al. never indicated how those genetic effects manifested themselves. Instead, McGue et al. neglected important, and inevitable, developmental effects that most developmental psychologists understand to influence parent and adolescent behavior. The author also suggests that there is great merit in adopting the approach of developmental systems theory in understanding McGue et al.'s findings in particular and all developmental phenomena in general.