Studies have found that individuals with bulimia nervosa can be classified into dietary and dietary-negative affect subtypes and that the latter exhibit greater eating pathology, psychiatric comorbidity, and functional impairment; a more protracted clinical course; and a worse treatment response. In this report, the authors describe 2 prospective studies that found that young women with threshold (n = 48) and subthreshold (n = 83) bulimic pathology can be classified into dietary and dietary-negative affect subtypes; that two subtyping approaches produced similar results (mean kappa = 0.94); that the subtyping distinction showed 4-week test-retest reliability (kappa = 0.61); and that the dietary-negative affect subtype showed greater eating pathology, emotional distress, functional impairment, treatment seeking, and lower likelihood of recovery over 6-month and 3-year follow-ups than the dietary subtype. The dieting-negative affect subtyping distinction evidenced greater test-retest reliability and concurrent and predictive validity than did the purging-nonpurging subtyping distinction. The additional evidence for the reliability and validity of this subtyping scheme, particularly the prognostic utility, suggests it is worth additional inquiry. (Contains 2 tables and 2 footnotes.)