We present a psychobiological approach to personality development, incorporating developmental principles outlined by R. B. Cairns (1979). We review individual differences in temperament and ask how a temperamental approach to personality might be congruent with these complex and flexible principles. We then illustrate the nature of temperamental processes by considering several developmental topics. We first consider the interaction of infant distress-proneness and maternal behavior in the development of attachment. We then describe the development of self-regulatory mechanisms, emphasizing development of conscience, aggression, and mastery motivation. Finally, we briefly review mechanisms of temperament and environment interaction, illustrating these processes through through variable developmental pathways for risk of adolescent and adult psychopathology. Throughout, we stress the idea that temperamental models of personality development are dynamic, interactive, and fit well with Cairns's developmental principles.