In this paper, we attempt to resolve these controversies by testing rational choice theories of participation with national survey panel data on political protest collected over time in the Federal Republic of Germany. Using individuals' reports of their actual participation in legal and illegal protest, and attitudes and perceptions measured before the behaviors in question, we test models of the causes and effects of individual protest participation on variables associated with several variants of rational choice theory. Our findings suggest that individual participation in protest is determined primarily by variables from what we term a collective interest model: individual preferences for public goods, perceptions of the importance of personal participation in collective efforts to achieve the good, and perceptions of the likelihood of group success. Variables associated with private material, social, or psychological "selective incentives" such as monetary payoffs, social pressure from significant others, and the expressive benefits of participation, are found to be less relevant as determinants of protest behavior. Moreover, several of the variables in the collective interest model are found to have a reciprocal relationship with protest behavior, as protest groups attempt to influence these perceptions and attitudes through the mobilization process itself. By contrast, the links between the selective incentives and participation, when they exist at all, are primarily unidirectional, as individuals adjust their current expectations of private rewards and costs in response to past participation in (or abstention from) collective protest activities. These findings have considerable implications for understanding both the dynamics of protest participation and the explanatory power of alternative versions of rational choice theories of collective behavior.(3)