Results indicated a reciprocal relationship between sexual assertiveness and sexual victimization. Specifically, women who reported a history of sexual victimization, particularly sexual victimization since age 14, had more difficulty refusing unwanted sexual advances. A lack of sexual assertiveness also predicted subsequent sexual victimization. Thus, women who exhibited low sexual assertiveness were more vulnerable to sexual victimization. The findings also revealed that the effects of sexual victimization on sexual assertiveness faded with time so that sexual assertiveness was most affected by more recent sexual victimization experiences. The results suggest that intervention strategies focused on strengthening sexual assertiveness may help reduce the risk of future sexual victimization. Participants were 937 women aged 18 to 30 years living in Buffalo, NY who were recruited for the study using random digit dialing between May 2000 and April 2002. Participants completed three waves of data collection, spaced 12 months apart, that included a face-to-face interview and two computer-assisted questionnaires. The interview and questionnaires focused on childhood sexual abuse, sexual victimization since age 14, recent sexual victimization, sexual assertiveness, depression, and post-traumatic stress disorder (PTSD). The relationship between sexual assertiveness and sexual victimization over time was examined using prospective path analysis. Future research should explore the processes affecting the development of sexual assertiveness. Figures, tables, references