The demobilisation of guerrillas and paramilitaries in Colombia, also known as irregular armed groups, has raised the question among mental health professionals as to whether ex-combatants who have had repeated exposure to stressful events might meet the requirements for posttraumatic stress disorder (PTSD). Upon arrival at a psychiatric clinic in Bogotá, 76 patients were evaluated by a group of mental health professionals with experience in this diagnosis. Contrary to clinicians' expectations, there was a conspicuous lack of PTSD among this population. Subsequently, the clinical team administered the Clinician Administered PTSD Scale with 21 of these patients; PTSD was found in 57% of the men. The authors consider various arguments that might explain this discrepancy. Differences between the clinical presentation of PTSD among the ex-combatants and the classic descriptions contained in the DSM-IV-TR may be explained by organisational characteristics of the irregular armed groups. Further research is necessary which focuses on the mental health of populations in the context of political violence, such as those encountered in Colombia.