Despite the fact that intimate partner violence (IPV) occurs within intimate relationships, we know relatively little about the characteristics of those intimate relationships, and even less about how IPV changes across time within different relationships. We use the Relationship Dynamics and Social Life (RDSL) study, based on a random sample of 1,003 18-19-year-old women residing in a Michigan county. Women were interviewed weekly for 2.5 years, resulting in an age range of 18 through 22. We estimate hybrid “within-between” regression models, which allows us to directly compare the same woman’s risk of experiencing IPV across her different relationships, varied in terms of resources, balance of power, conflict, childbearing, relationship type, and duration. Our analyses demonstrate that power imbalance in intimate relationships, non-monogamous and unstable relationships, relationships with men who are not the father of a woman’s existing children, and serious relationships (especially stayover and cohabiting) place young women in their late teens and early twenties at particularly high risk of multiple dimensions of IPV. Our fixed-effects modeling strategy isolated the increase in IPV risk that is due to these characteristics and experiences within intimate relationships from the risk due to young women being at high risk of IPV for other reasons who might tend to choose these types of relationships. The elevated risk of IPV in relationships with these characteristics and experiences supports a causal link between them. Our research supports the potential efficacy of interventions that reduce conflict, equalize power within relationships, and encourage women—especially young mothers—to delay serious relationships.