The current study used factor analysis to assess the degree to which personality characteristics derived from different theories signify the same latent personality constructs, and biometric modeling to understand the genetic and environmental structure of these constructs. Participants were drawn from the Twin and Offspring Study in Sweden (TOSS), and included 318 male twin pairs (129 Monozygotic, 189 Dizygotic) and 544 female twin pairs (258 Monozygotic, 286 Dizygotic). Personality characteristics were assessed via two self-report measures: the Temperament and Character Inventory and the Karolinksa Scales of Personality. Factor analyses identified three personality factors for male and female twins: anxiety, aggression, and sociability. In addition, selfregulation tendencies were integrated within each factor. Biometric analyses indicated that these latent factors were heritable (h 2 ranged from .52 to .67). Most personality characteristics that contributed to each latent factor also demonstrated unique genetic influences. Collectively, these findings underscore the complex nature of aggressiveness, anxiousness, and sociability, and indicate that scales that are conceptually similar may assess genetically distinct systems.