A population of the fire fighters who had been exposed to a natural disaster were screened using the General Health Questionnaire 4, 11, and 29 months after a natural disaster. On the basis of these data, a high-risk group of subjects who had scored as cases and probable cases and a symptom-free comparison group were interviewed using the Diagnostic Interview Schedule 42 months after the disaster. The prevalence of posttraumatic stress disorder (PTSD), affective disorders, and anxiety disorders was examined. Only 23% of the 70 subjects who had developed a PTSD did not attract a further diagnosis, with major depression being the most common concurrent disorder. Comorbidity appeared to be an important predictor of chronic PTSD, especially with panic disorder and phobic disorders. The subjects who had only a PTSD appeared to have had the highest exposure to the disaster. Adversity experienced both before and after the disaster influenced the onset of both anxiety and affective disorders.