Within a psychotherapy development research project, thirty male (50%) and female (50%) personality disordered outpatients receiving methadone maintenance were randomly assigned to receive one of two 6-month manual-guided individual psychotherapies, Dual Focus Schema Therapy (DFST) or 12 Step Facilitation Therapy (12FT). All participants met diagnostic criteria for at least one personality disorder with antisocial, borderline, avoidant, and dependent being the most common. There were no significant differences between the two therapies for retention, utilization, or reductions in psychiatric symptoms or psychosocial impairment. Both therapy conditions demonstrated significant reductions in various severity indicators. Participants demonstrated more rapid decreases in the frequency of their substance use over six months of DFST in comparison to 12FT. DFST also was associated with a stronger therapeutic alliance between therapists and participants. Contrary to predictions, 12FT demonstrated better reduction of dysphoric affect than did DFST. DFST shows initial promise as the first time-limited manual-guided psychotherapeutic approach for the full range of personality disorders encountered in substance abuse patients.