Because diet is a key issue in the treatment of diabetes mellitus, it is assumed that these patients are prone to eating disorders. In a multicenter study, we have therefore assessed the prevalence of eating disorders in 662 patients with insulin dependent diabetes mellitus (IDDM) (n = 340) and non-insulin-dependent diabetes mellitus (NIDDM) (n = 322). A two-stage study combining self-rating questionnaires and a standardized interview was carried out. We found a prevalence of eating disorders of 5.9% (lifetime prevalence of 10%), irrespective of gender and type of diabetes; 4.1% of the whole sample reported intentional insulin undertreatment or omission. When patients were stratified according to IDDM and NIDDM, there was no difference in the prevalence of all eating disorders (point prevalence 5.5% vs. 6.5%, lifetime prevalence 10.0% vs. 9.9%). Prevalence of bulimia nervosa (BN) was more frequent in IDDM patients (point prevalence 1.5% vs. 0.3%, lifetime prevalence 3.2% vs. 1.9%) and binge eating (BED) was more frequent in NIDDM patients (point prevalence 1.8% vs. 3.7%, lifetime prevalence 2.6% vs. 5.9%). We conclude that eating disorders seem to be equally frequent in IDDM and NIDDM patients. However, there might be different features of eating disorders in both types of diabetes.