PROJECT SUMMARY Sexual assault is a significant public health problem. The sequelae of victimization involve both mental and physical health problems (Bedard-Gilligan et al., 2011; Hughes et al., 2010), and once victimized, women are at significant increased risk for revictimization (Classen et al., 2005; Messman-Moore & Long, 2003). Sexual assault has reached epidemic proportions on college campuses, with undergraduate women reporting high rates of victimization (Krebs et al., 2007). Alcohol use is intimately intertwined with sexual violence (Abbey, 2011), as well as high-risk sexual behavior (Scott-Sheldon et al., 2010). Work on the situational precipitants of sexual assault has relied primarily on women's retrospective accounts, even though autobiographical memory is plagued by error (Bradburn et al., 1987). One way to obtain ecologically valid observations of these precipitants may be through Ecological Momentary Assessment (EMA). EMA data are collected in near real- time and are considered to have greater validity than retrospective accounts (Shiffman et al., 2008). The primary aim of this study will be to use EMA to obtain a better understanding of the contextual determinants of sexual assault, as well as the co-occurrence of victimization, risky sex, and substance use. This basic work then will inform the development of an Ecological Momentary Intervention (EMI) for college women to reduce their risk. EMI would permit an opportunity to intervene prior to and during high-risk situations by providing women with personalized feedback about their level of risk for victimization and related adverse events. The secondary aim of this study will be to conduct a randomized controlled trial (RCT) comparing the effectiveness of EMA/EMI, relative to EMA-only and an assessment only control group, in decreasing rates of sexual assault, risky sexual behavior, and substance use. This RCT will be prospective in design and target women who are at increased risk for assault (freshman). If supported, this work would offer college campuses a cost-effective, easily disseminated approach to preventing assault and other adverse consequences.