Ethical standards are core components of practice standards and codes of conduct for mental health practitioners. Practice standards and ethics related to boundaries are generally based on historical review, study of mental health services, and the impact of boundary crossing or boundary violations on clients receiving services. This article explores some common standards of ethical practice related to boundaries and dual or multiple relationships between mental health professionals and clients. The underlying conceptual basis for these standards and examples of questions encountered in clinical practice with sexual offenders are explored.