In order to determine the reasons for which a person enters an illegal armed group in Antioquia, the existing literature at both international and national level was reviewed. This was checked against existing quantitative information from victims and ex-victimaries at national and departmental level, and qualitative information found in interviews with members of criminal gangs and in focal groups with experts. A subject may have motivations to commit themselves based on coercion, individual wishes, targeted incentives, social and family environments, grievances, lack of social control, and personal characteristics or traits that can make it more likely to engage in criminal activities. Their continuation in an armed group will depend on the coupling strategies that may consist of incrimination, economic predictions, ideological discourse, or threats. After a process of demobilisation, other factors such as personal insecurity, lack of political influence, lack of social prestige, economic insecurity and other specific failures of the process of reintegration into society may influence reoffending in criminal activities. In Antioquia, coercion as a recruitment strategy continues to be used; motivations based on social environments were seen as essential and common for criminal gangs and guerrilla groups; individual wishes focused on the interest in a military life were more related to guerrilla, and coaguous feelings were more associated with criminal gangs; targeted incentives through wage promises were specific to criminal gangs; finally, grievances, which are ideological support specific to the guerrilla, are also used by criminal gangs as a strategy to recruit and seek legitimacy in the territories in which they seek to consolidate. With the purpose of determining the causes by which a person trainees a member of an illegal armed group in Antioquia, existing national and international literature was reviewed. This literature was compares to the quantative information related to perpetrators and former perpetrators in the country and in the State, and the qualitative information found in relation to members of criminal bands and focal groups with experts. An individual can have good reassignments to commit crimes based on Coercion, individual wishes, selective incentives, social and family environments, damages, lack of social control, and on severe personal characteristics or traits which may make of him more prone to commit criminal activities. HIS continuation in an armed group will depend on the enhancement strategies that can involve Incrimination, economic benefits, ideological speech or threats. After a demobilisation process, other factors as personal insecurity, no of political influence, absence of social prestige economic insecurity, and other specific failures of the process of reintegration to society may result in the person’s new perpetration of criminal activities. In Antioquia, Coercion as a reinforcement strategy is still a frequently used method; basic motivations in social environments were observed as essential and common for criminal bands and guerrilla groups; individual intent fostered on the interest for a military life were more related to guerrilla and avarious feelings were more associated to criminal bands; elective incentives after advocating a salary were factors related to criminal bands; finally, damages, that are an ideological support of guerrilla groups are also used by criminal banks as a strategy for enhancement and a search for legitimacy within the territories where consolidation is sought.