What determines the recidivism of ex-combatants from armed conflicts? In postconflict settings around the world, there has been growing interest in reintegration programs to prevent ex-combatants from returning to illegal activities or to armed groups, yet little is known about who decides to "go bad." We evaluate explanations for recidivism related to combatant experiences and common criminal motives by combining data from a representative survey of ex-combatants of various armed groups in Colombia with police records of observed behaviors that indicate which among the respondents returned to belligerent or illegal activities. Consistent with a theory of recidivism being shaped by driving and restraining factors, the results suggest that factors such as antisocial personality traits, weak family ties, lack of educational attainment, and the presence of criminal groups are most highly correlated with various kinds of recidivism and hold implications for programs and policies to successfully reintegrate ex-combatants into society.