Although behavioral risk factors such as substance use have been hypothesized to increase women's vulnerability to sexual victimization, prospective studies provide mixed empirical support. In the current prospective study, the authors considered substance use, sexual activity, and sexual assertiveness as predictors of sexual victimization from intimate partners and nonintimate perpetrators. Among a representative community sample of women ages 18-30 years (N = 927), 17.9% reported sexual victimization over 2 years, the majority by an intimate partner. Low sexual refusal assertiveness, drug use, and prior intimate partner victimization predicted intimate partner sexual victimization. Heavy episodic drinking and number of sexual partners predicted victimization from nonintimates. The finding that there are different risk factors for sexual victimization from intimates versus nonintimates suggests the need for tailored prevention strategies.