We examined various components of the 'borderline personality construct' as predictors of initial response to treatment in 61 bulimic patients. At pre-treatment, a 'borderline/non-borderline' distinction was established using DSM III-R criteria, and other components of 'borderline' pathology ('borderline traits', object-relations disturbances, maladaptive defences and mood pathology) were assessed using self-report. Self-reported eating and psychiatric symptoms were obtained at initial and three-month evaluations. Using hierarchical regression analyses, we controlled effects of initial eating and psychiatric symptoms, and then evaluated various measures of the borderline construct as predictors of later symptom severity. Categorical borderline PD diagnoses were linked to poorer response on eating attitudes and symptoms, and fine-grained analyses indicated that this prognostic effect might be mediated by mood and object-relations disturbances. Findings therefore seemed to isolate specific subcomponents of borderline personality pathology that predicted poorer response on eating symptoms.