We hypothesized that an interpersonal trait approach would improve our understanding of the behavioral manifestations of basal testosterone. Participants provided saliva samples for testosterone assays on two separate visits and completed the Interpersonal Adjective Scales, the Circumplex Scales of Interpersonal Values, and measures of attachment and loneliness. High testosterone was associated with a distinct interpersonal style that included: attachment-related avoidance, dominance, and disconnectedness. High testosterone was also associated with loneliness, and this relationship was mediated by attachment-related avoidance. These findings add to our understanding of the interrelationships between hormones, personality, and social behavior. The circumplex structure revealed by testosterone's associations provides evidence for its construct validity as a biological marker of an interpersonally dominant, cold, avoidant, and lonely interpersonal style. © 2014 Elsevier Inc.