Although both marital and cohabiting unions fall under the rubric of family, this article contends that this does not justify the equation of cohabiting unions to marriages. This review shows that, despite methodological inconsistencies, representative sample studies consistently evince a higher rate of violence among cohabiting couples than marital unions. As well, both representative and nonrepresentative sample indicators show that violence in cohabiting unions is more likely to be severe than violence that occurs in marital unions. This indicates that the practice of combining married couples and cohabiting couples may be unnecessarily obfuscating the understanding of the causes of violence against women. More research is needed to identify whether the causal pathways leading to violence against women differ between married couples and cohabiting couples in a manner that is consistent with qualitative differences between these two types of relationships. To guide this work, the authors have proposed a number of explanatory frameworks for understanding higher rates of violence among cohabiting couples, emphasizing an application of Berger and Kellner's (1994) thesis to the study of selection and relationship factors. 2 tables, 1 figure, and 63 references