The role of stressful life and difficulties in the onset of insulin-dependent (Type 1) diabetes mellitus was examined in a group of 13 newly diagnosed diabetics and sibling and neighbourhood controls. Subjects aged between 17-34 years, were interviewed and information was collected over the 3 year period preceding clinical diagnosis of diabetes. Diabetics had a higher frequency of one or more severe life events prior to diagnosis i.e. 77% compared with their siblings and age/sex matched controls i.e. 39% and 15% respectively. Diabetics also had a higher percentage of 2 or more severe life events prior to diagnosis i.e. 54% compared with 8% for siblings and 8% for neighbourhood controls. The frequency of severe difficulties was also higher for diabetics--46% compared with 13% and 23% for siblings and neighbourhood controls respectively. Stressful events and difficulties may be triggering factors involved in the aetiology of insulin-dependent diabetes.