A validation study of 30 married females and 30 married males was conducted on a theoretical model of stages in interpersonal development developed by Bar-Yam Hassan (Bar-Yam Hassan & Bar-Yam, 1987). According to the model, the five stages of adult interpersonal development are: (1) Social Relatedness versus Self-Insistence, or need for Approval; (2) Affiliation versus Exclusion, or need for Affiliation; (3) Belonging versus Alienation, or need for Belongingness; (4) Intimacy versus Isolation, or need for Intimacy; and (5) Interdependence versus Interpersonal Constriction, or need for Reciprocity. Interview data were scored for the subject's orientation to relationships, nature of interpersonal interactions, and interpersonal need. The present study examined in more depth the qualitative nature and process of interpersonal development in young adulthood from this same sample. Questions were raised regarding the characteristics of interpersonal development in young adults, both cross-sectionally and longitudinally, as well as the factors which may contribute to change in interpersonal development over time. Results generally support a developmental conception of interpersonal relatedness in young adulthood as involving a progressive sequence of transformations in the qualitative nature of interpersonal relationships. (Tables are provided of stages of interpersonal development across the life span, and in young adulthood. Ten references are included.) (TE)