Based on 42 in-depth interviews with members of three former Colombian guerrilla organizations, M-19, EPL, and CRS, reasons why they stayed in these organizations through several years, if not decades, of violent confrontation with government forces are examined. From a micro-level perspective, the study identifies four important motivations for members to remain in these groups: personal dependence on their organization, values shared with other members and with the group, the clandestine life-style, and self-identity, which is boosted by the subjects' feeling that their work in the group matters.