The present study investigates the demographics of same-sex marriages—that is, registered partnerships—in Norway and Sweden. We give an overview of the demographic characteristics of the spouses of these partnerships, study patterns of their divorce risks, and compare the dynamics of same-sex couples with those of heterosexual marriages. We use longitudinal information from the population registers of the two countries that cover all persons in partnerships. Our demographic analyses include information on characteristics such as age, sex, geographic background, experience of previous opposite-sex marriage, parenthood, and educational attainment of the partners involved. The results show that in many respects, the distributions of married populations on these characteristics differ by the sex composition of the couples. Patterns in divorce risks are rather similar in same-sex and opposite-sex marriages, but divorce-risk levels are considerably higher in same-sex marriages. The divorce risk for female partnerships is double that for male partnerships.