[영문]This study explores how cohabitation differs for older and younger adults, drawing on data from 966 cohabitors in each of the first 2 waves of the National Survey of Families and Households. Older cohabitors report significantly higher levels of relationship quality and stability than younger cohabitors, although they are less likely to have plans to marry their partners. Few differences were found in the reasons to cohabit, although assessing compatibility is a more important reason for younger cohabitors. Findings suggest that older cohabitors are more likely to view their relationship as an alternative to marriage, whereas younger cohabitors are more likely to view their relationship as a prelude to it.