This article proposes and argues for the importance of a distinction between "low-" and "high-risk/cost activism" and outlines a model or recruitment to the latter. The model emphasizes the importance of both structural and individual motivational factors in high-risk/cost activism; contending that an intense ideological identification with the values of the movement disposes the individual toward participation, while a prior history of activism and integration into supportive networks acts as the structural "pull" encouraging the individual to make good on his or her strongly held beliefs. The utility of the model is then analyzed in relation to a single instance of high-risk/cost activism: the 1964 Freedom Summer project. Data from project applications for 720 persons who actually went to Mississippi, as well as from 241 "no shows," are used to explain the applicants' chances of participation in terms of various factors. The results of this analysis generally confirm the importance of microstructural factors in recruitment to the campaign. Participants were distinguished from withdrawals primarily on the basis of their (a) greater number of organizational affiliations, (b) higher levels of prior civil rights activity, and (c) stronger and more extensive ties to other participants.