According to the basic assumption underlying this article, people are more likely to participate in protest the more they feel that a group they identify with is treated unjustly. Depersonalization and the politicization of group identification are discussed as two processes that mediate the relationship between group identification and protest participation. Empirical evidence from three studies is discussed. In a study among people older than 55, participation in unions for the elderly appears to be correlated strongly with identification with the elderly. In a study of participation in peaceful protest among South African citizens, indicators of identification appeared to be correlated with protest participation, and finally, Dutch farmers were more likely to participate in farmers' protest the more they identified with other farmers. Results from the latter, longitudinal study suggest a recursive relationship between identity and protest participation: Group identification fosters protest participation and protest participation reinforces group identification.