To present the twelve-year outcome of binge eating disorder (BED) in 68 female inpatients compared to bulimia nervosa, purging type (BN-P; N = 196). Self and expert ratings focused on the beginning of therapy and the 12-year follow-up. 36% of BED and 28.2% of BN-P patients still received an eating disorder diagnosis at follow-up. Differences between groups were small (Eating Disorder Inventory, Structured Inventory for Anorexic and Bulimic Syndromes, Hopkins Symptom Checklist, Beck Depression Inventory). Similar predictors for BED and BN-P were identified. Psychiatric comorbidity was the predominant predictor of poor outcome in both diagnoses. Predictors for BED outcome were body dissatisfaction, sexual abuse, and impulsivity; self-injury predicted BN-P outcome. Course, outcome, and mortality were similar for BED and BN-P. Both disorders had psychiatric comorbidity as the main predictor of outcome, and there was a diagnostic shift between BED and BN-P over time, pointing to their nosological proximity. Data are relevant for the formulation of DSM-V and ICD-11 diagnostic criteria.