This study investigated the relationship between Bowen's (1978) concept of differentiation of self and Erikson's (1950Erikson's ( / 1963 psychosocial stages of development. Three hundred and fourteen university undergraduates completed the Measure of Psychosocial Development (MPD; Hawley, 1988) and the Differentiation of Self Inventory (DSI; Skowron & Friedlander, 1998). Multiple regression analyses indicated that differentiation level is significantly predictive of psychosocial development. Clinical implications of the findings are discussed. KEY WORDS: differentiation of self; psychosocial development; Bowen theory.Bowen (1976, 1978) family systems theory is a prominent and widely used approach in the marriage and family therapy field. The major tenets of the theory, including differentiation of self, triangulation, family projection process, fusion, emotional cutoff, and multigenerational transmission process, are foundational concepts in the training of many marriage and family therapists, with differentiation being the most central concept in Bowen's theory.