Part 1 The study of mental health - methods and illustrations: introduction; mental health; the men of the Grant study; how they were studied; health redefined - the joyful expression of sex and of anger. Part 2 Basic styles of adaptation: adaptive ego mechanisms - a hierarchy; sublimation; suppression, anticipation, altruism and humour; the neurotic defenses; the immature defenses. Part 3 Developments consequences of adaptation: the adult life cycle - in one culture; paths into health; successful adjustment; the child is father to the man; friends, wives and children. Part 4 Conclusions: the maturing ego; what is mental health - a reprise; a summary. Appendices: a glossary of defenses; the interview schedule; the rating scales.