This chapter discusses the physical and cognitive changes characteristic of pubertal maturation. Just prior to puberty, the sensitivity of the gonadostat to the negative feedback of gonadal sex steroids decreases, releasing the hypothalamic-pituitary axis (HPA) from inhibition. Puberty is heralded by the myriad of physical changes that occur in the body with the advent of the hormonally mediated effects and the cognitive shift associated with them. With both the psychological and biological maturity of adolescence come issues of separation and individuation, consolidation of a sense of self, development of a sexual identity and progress toward academic and vocational plans for adult life. The most useful framework for the discussion is the biopsychosocial model, which has also been used successfully in so many other domains. Throughout adolescence, the work of development that was made possible by the physical, cognitive and psychological changes induced by puberty continues unabated.