This study investigated the relative contributions of gender and sexual orientation as factors associated with the formation of boundaries in dyadic intimate relating in both same- and opposite-sex couples. The study examined a relational pattern previously not empirically investigated but widely accepted as an actuality unique to lesbians; specifically, that lesbians tend to remain connected to ex-serious-relationship partners after breakup. The study utilized a research design approach emphasizing the methodological utility and heuristic value of including sexual orientation as an independent variable in studies of gender dynamics. Two general classes of theoretical frameworks, those emphasizing gender role socialization influences and those emphasizing systems influences, were discussed in terms of their relative goodness of fit as conceptual bases for the data. Questionnaires were completed by 60 lesbians, 37 gay men, 45 heterosexual women, and 39 heterosexual men. Lesbians and gay men reported higher levels of connection to ex-serious-relationship partners than heterosexuals. The data reflect how inclusion of sexual orientation can broaden understandings of gender differentiated phenomena beyond more traditional gender-only based accounts.