The author addresses the issue of sexual relations between therapist and patient and the related boundary violations that are involved in such relations. He points out that patients with borderline personality disorder are particularly likely to evoke boundary violations, including sexual acting out. These patients apparently constitute the majority of patients who falsely accuse therapists of sexual involvement. Therapists who are aware of patterns of errors in therapy and countertransference--through education, anticipation, and forewarning--can avert the serious outcomes that result from these errors.