Fifty preschool children from 47 Iranian families living as refugees in Sweden were assessed individually, simultaneously with parental interviews focusing on exposure to organized violence and post-traumatic stress symptomatology in the children. Information given by the children increased the prevalence of a Post-Traumatic Stress Disorder (PTSD) diagnosis (DSM-III-R) from 2% to 21% in the 42 children with traumatic exposure through war and political persecution. The amount of traumatic exposure was strongly related to the prevalence of PTSD. The stability of prevalence was high in a follow-up 2 and 1/2 years later; 23% of the children with traumatic exposure still met the full criteria of PTSD according to DSM-III-R.