Using data from 2,898 women from the National Longitudinal Survey of Youth-1979, we employ a novel method to examine two perspectives, social selection and the experience of cohabitation, commonly used to explain the negative relationship outcomes cohabiting women report. Results reveal cohabitation is negatively related to marital happiness and communication and positively related to conflict. As in previous research, selection mechanisms appear to increase the odds of cohabitation while decreasing marital happiness. A closer examination of the problem also reveals a negative effect of the experience of cohabitation. This paper's primary contributions are the ability to model selection and experience in the same model and evidence of a robust effect of cohabitation on marital quality. These results underscore the complex pathways between union formation, family structure and marital outcomes.