We argue that lexical studies of personality structure suggest the existence of six major dimensions of personality: (I) Surgency, (II) Agreeableness, (III) Conscientiousness, (IV) Emotional Stability, (V) Intellect/Imagination, and (VI) Honesty. We then propose a two-part theoretical basis for these dimensions. First, Honesty and rotated variants of Agreeableness and Emotional Stability are interpreted in terms of three traits—fairness/non-exploitation, forgiveness/non-retaliation, and empathy/attachment—that underlie prosocial versus antisocial tendencies. Second, the Surgency, Conscientiousness, and Intellect/Imagination factors are interpreted as traits that involve active engagement within three domains of endeavour—social, task-related, and idea-related endeavour. Predictions that follow from these interpretations are tested and found to be supported. Copyright © 2001 John Wiley & Sons, Ltd.