This study was a 3-year follow-up of 65 male and 138 female same-sex couples who had civil unions in Vermont during the 1st year of that legislation. These couples were compared with 23 male and 61 female same-sex couples in their friendship circles who did not have civil unions and with 55 heterosexual married couples (1 member of each was a sibling to a member of a civil union couple). Despite the legalized nature of their relationships, civil union couples did not differ on any measure from same-sex couples who were not in civil unions. However, same-sex couples not in civil unions were more likely to have ended their relationships than same-sex civil union or heterosexual married couples. Compared with heterosexual married participants, both types of same-sex couples reported greater relationship quality, compatibility, and intimacy and lower levels of conflict. Longitudinal predictors of relationship quality at Time 2 included less conflict, greater level of outness, and a shorter relationship length for men in same-sex relationships and included less conflict and more frequent sex for women in same-sex relationships at Time 1.