The primary objectives of this research are to define intimacy more distinctly (including what constitutes greater depth or higher levels of intimacy); to explore the changes across adult life; and most importantly, to assess the respective degree of association intimacy has with adaptation to life stress. A series of studies were undertaken to define and operationalize the concept of intimacy. The results produced 16 items that defined the parameters of intimacy and provided the content for the intimacy instrument. A sample of 35 professional judges rank-ordered the 16 intimacy dimensions for their degree of importance in an ideal opposite-sex and same-sex relationship. Life stress was measured by the Life Events Questionnaire, and adaptation was assessed by the General Morale Index and a 42-item psychosomatic symptom checklist. A sample of 171 men and women was selected from the San Francisco Human Development Research Program's Longitudinal Study of Transitions. Each was experiencing one of four major life transitional stages. The research results support the notion that once a minimum level or threshold of intimacy is established between older married couples, it then has the power to intervene or buffer one from the stresses accompanying the aging process. (Author)