This study uses data from the Norwegian NorLAG study (N = 2,455) to examine differences in relationship quality and psychological well-being between middle-aged cohabitors and married persons. The authors question whether previous results linking cohabitation as compared with marriage to lower well-being will replicate in Norway, where cohabitation is much more widespread and socially accepted and where the legal system increasingly treats cohabitation and marriage as equal. The authors find that never-married cohabitors but not formerly married cohabitors report lower levels of relational and subjective well-being compared with their married counterparts. In this way, cohabitation per se is not qualitatively different from marriage. The presence of children and union duration have previously been linked to greater discontentment among cohabitors, but this is not evinced in this study. (Contains 4 tables and 1 figure.)