In the present investigation, Murray Bowen's (1978) theoretical propositions about the relationship between differentiation of self and quality of marital relationships were tested. Couples' levels of differentiation explained substantial variance in marital adjustment: 74% of variance in husband marital adjustment scores and 61 % of variance in wife marital adjustment scores were accounted for by couple differentiation of self-scores. Greater husband emotional cutoff uniquely accounted for husband and wife marital discord. Contrary to family systems theory, actual couples were no more similar on differentiation than were randomly matched couples. Finally, greater complementarity among couples along the specific dimensions of emotional cutoff and emotional reactivity predicted greater marital distress. In the last 2 decades, interest in families and family therapy has grown dramatically among counseling psychologists (e.g., Gelso & Fretz, 1992; Fitzgerald & Osipow, 1988; Schneider, Watkins, & Gelso, 1988). Increasingly, counselors are turning to family systems theories to understand how adults seek out, create, and maintain mutually satisfying intimate relationships and to enhance treatment strategies. Yet family systems theories and constructs tend to receive little attention from marital researchers, who instead tended to focus their efforts on elucidating the role that pleasant and aversive behavioral exchanges, communication skills, and problem solving play in marital functioning (cf. Gottman, 1998; Jacobson & Addis, 1993). In contrast, practicing clinicians often employ family systems therapies to treat marital and family disorders (Gelso & Fretz, 1992; Nichols & Schwartz, 1998) but with little evidence to support the veracity of their systemic formulations of how marital problems are developed and maintained. In light of the interest in family systems theories among counseling psychologists and evidence suggesting couple and family therapy is effective (e.g., Baucom, Shoham, Mueser, Daiuto, & Stickle, 1998; Gurman, Kniskern, & Pinsof, 1986), greater efforts must be undertaken to examine and test the central constructs and propositions of major family systems approaches. The purpose of the present study was to examine the utility of Bowen family systems theory for predicting quality of married life.