A theoretical model of rape law impact is developed, and the effects of several reform measures on official rape rates are examined through multiple regression analyses that control for contextual and etiological factors. The results show that rape law reform is for the most part unrelated to rape rates, although there are departures from this pattern. In particular, there are significant effects of an index of definitional reforms and a variable that measures the criminalization of nonconsensual sexual contacts not involving clearly demonstrable force or other extreme circumstances. There are also interactive effects between law reform and contextual variables, as well as direct effects of contextual and etiological variables. The findings show that law reform should not be viewed as the most significant step in reducing the problem of rape. Nevertheless, the limited effectiveness of reform does not warrant its complete dismissal, because the findings suggest some impact on official rape rates. The elements of reform most likely to increase these rates are the Definition and Nonconsensual Contact reforms that broaden the range of offenses covered by law. Apparently, the widened net of criminalization has resulted in reporting increases and higher apprehension rates. In addition, the negative associations between "Nonconsensual Contact" and official rape rates suggest a preventive-deterrent impact that requires examination in future research. This study also has implications beyond rape law reform. The findings on the postreform contextual effects of the police variables underscore the role of social context in moderating or filtering the impact of law reform. The results regarding prereform liberalism-feminism suggest the need for a model of legal impact that considers law reform as both a product and a cause of social change. Finally, the findings on etiological variables and rape crisis centers underscore the need to consider nonlegal factors that influence the behavior being investigated in legal impact research. 1 table and 72 references