Prior research on victim self-protective behavior (VSPB) has largely been void of a theoretical basis. Accordingly, it remains unclear why it would be expected that victim actions might mitigate crime incident outcomes or under which circumstances such actions might be most successful. Using data from the National Crime Victimization Survey for periods 1992 to 2004, this study uses a nested logistic regression analysis to test the predictive utility of opportunity theory in explaining outcomes of VSPB during incidents of robbery and rape. The results suggest that opportunity theory provides a useful framework for understanding the effect of victim resistance on crime outcomes. Greater levels of victim resistance increase the effort needed by offenders, resulting in some cases in a 93% and 92% decrease in the odds of a robbery and rape being completed, respectively, compared to when no resistance is used. Implications for crime prevention practice are discussed. (Contains 7 notes and 4 tables.)