Traumas are frequently overlooked in general psychiatric settings and PTSD is underestimated. Such findings indicate the need to conceptualise trauma in terms of multiple events and to examine the aetiology of PTSD amongst patients in everyday psychiatric practice. The present study examines aetiological factors of PTSD in 3 minority groups at a general psychiatric outpatient clinic--Arabs, Iranians and Turks selected from an entire year's cohort of patients--and a sample of Swedish patients of similar age and gender distribution. Histories were collected from 115 patients, both regarding their own traumas and traumas involving relatives and close friends, by means of a questionnaire. A self-rating instrument for PTSD was used in order to study the relationship between trauma and PTSD outcome. Of the patients, 89% had experienced at least one trauma, and 77% multiple traumatic events. The prevalence of probable PTSD varied between ethnic groups: Iranians 69%, Arabs 59%, Turks 53% and Swedes 29%. In a logistic regression analysis, probable PTSD outcome was associated with multiplicity of relatives' traumas, multiplicity of own traumas and belonging to an ethnic minority, but not with gender. No patient without a trauma history was positively assessed for probable PTSD.