Although there has been considerable discussion of boundary excursions in clinician-patient relationships, little empirical research exists. This pilot study adds to the existing theoretical discussion by comparing perceptions by mental health professionals in Brazil and the United States of what may constitute boundary violations. Participants rated each possible boundary violation according to its degree of harm and professional unacceptability. Three distinct groupings of boundary violations were found: (1) core, consisting of the most serious violations; (2) separation of therapist and client lives, involving encounters between therapists and clients outside of therapy; and (3) disclosure and greeting behavior, involving disclosure of information about the therapist and greeting behavior. The U.S. and Brazilian perceptions were found to be surprisingly similar, with only a few differences.