The interpersonal circumplex describes two major axes of personality that guide much of social behavior. Agency, one half of the interpersonal circumplex, refers to relatively stable behavioral patterns that center on self-focused dominance and assertiveness assessed in terms of goals, values, or personality traits. However, the psychometric overlap between agency and the most closely linked big five dimension, extraversion, is not well-established, and little behavior genetic work has documented evidence concerning the role of genetic and environmental influences on trait agency. We used the Midlife Development in the United States study to examine agency, big five, and generativity with replication and robustness checks (N