Childhood traumatic experiences, rearing styles, familial mental disorders and birth risk factors have been associated with the development of social anxiety disorder. Patients with social anxiety disorder (n=50) and healthy controls (n=120) were investigated using a retrospective interview with 203 questions. The frequency of reports of traumatic childhood experiences was significantly higher in patients than in controls, including separation from parents, parents' marital discord, sexual abuse, familial violence, childhood illness, and other factors. On a 0-10 point 'severe trauma scale' patients had significantly higher mean scores (2.0; SD 1.28) than control subjects (0.82; SD 1.1; p<0.0001). Only 6 (12%) of the social phobic patients, but 63 (52.5%) of the controls did not report any severe traumatic events at all (chi2=24.0; p<0.0001). Compared to controls, patients described their parents' rearing styles as significantly more unfavourable. Patients reported higher rates of psychiatric disorders in their families in general, in particular anxiety disorders, depression, and suicidality. Birth risk factors did not differ between patients and controls. In a logistic regression model, the highest contribution was noted for familial anxiety disorders. Separation from parents also had a significant, but smaller influence. There was only a trend towards a significant contribution of childhood sexual abuse. Violence in the family, parental rearing styles and birth risk factors did not contribute significantly. The present data suggest that the aetiology of social anxiety disorder is multifactorial and that familial mental disorders and separation experiences are the most important contributing factors.