Relationship satisfaction, affect, and stress were examined in 313 same-sex couples who had had civil unions in Vermont during the first year of this legislation. Similarity between partners on age and on positive/negative affectivity was related to relationship satisfaction whereas there was no association with similarity in income, education, and outness. Lesbian couples (n=199), compared to gay male couples, reported experiencing more stress related to family reaction to their sexuality, whereas gay male couples (n=114) reported more stress surrounding the issues of HIV/AIDS and violence/harassment than did lesbian couples. This study is the first to examine within-couple factors among same-sex couples with legalized relationships.