The aims of this study were to examine the incidence and risk factors of major depression, bipolar disorder, psychoactive substance use, psychotic and anxiety disorders in relation to post-traumatic stress disorders (PTSD) in a study group exposed to two different traumatic events, i.e. 128 fire and 55 motor vehicle accident victims. Data have been collected 7-9 months after the traumatic event. The diagnosis of axis-I diagnoses, other than PTSD, was made according to DSM-III-R criteria using the Structured Interview according to the DSM-III-R. The incidence of new-onset major depression was 13.4%, generalised anxiety disorder (GAD) 12.6 %, agoraphobia 10.2% and psychoactive substance use disorders 6%. Simple phobia, panic disorder and obsessive compulsive disorder had a much lower incidence (< 2.0%). Fifty-one percent of the victims with PTSD had one or more additional axis-I diagnoses, major depression (26.2%), agoraphobia (21.0%) and generalised anxiety disorder (24.6 %) being the most common. Physical injury was the single best predictor for major depression. The best predictors for the development of new-onset anxiety disorders, other than PTSD, were: type and horror of the trauma, the extent of physical injury, the loss of control during the traumatic event, contextual stimuli, younger age and female sex. comorbid disorders, such as depression, GAD and agoraphobia, commonly occur within the first few months after man-made accidental traumata. Trauma variables, which are known to be related to the development of PTSD, are also related to the occurrence of these comorbid disorders.