The ego mechanisms of defense (both "coping" and "defensive") were observed in the life-styles of 30 men over a 25-year period of prospective follow-up. The results suggest that most ego mechanisms of defense, although first described in pathologically abnormal populations, can be observed in an adult population specially selected for "health." For some individuals a fixed constellation of defensive styles persisted for decades. For others, choice of ego mechanism appeared to evolve parallel to a maturing life adaptation. Because of prolonged follow-up it was possible to define with some assurance the relative success of occupational, marital, and medical adaptation. Theoretically mature choices of ego mechanisms appeared clinically correlated with the more successful life adjustments.