We investigate change in the association between premarital cohabitation and the risk of separation. Using retrospective marriage history data from the first wave (2001) of the Household Income and Labor Dynamics in Australian survey, we examine 6,210 first marriages formed between 1945 and 2000. We find the association between premarital cohabitation and separation is changing. The increased risk of separation for cohabitors compared to noncohabitors diminishes each year for marriages before 1988. This association then reverses for marriages after 1988, where noncohabitors have an increased risk of separation. Our results indicate that, for more recent marriages, premarital cohabitation reduces the risk of separation; more research is needed to understand the underlying mechanisms for this reversal.