This Chapter delves into the ethical and legal dimensions of the physician-patient relationship, beginning with its historical development worldwide and its specific evolution under Brazilian law. It first examines the contractual nature of medical services in Brazil, with a focus on how physician’s duties of conduct impact these contractual relationships. A comprehensive analysis of Brazilian case law provides insight into the reinterpretation of these duties, particularly concerning disclosure, loyalty, and patient protection, highlighting the legal consequences of breaching them, especially in cases involving informed consent. Expanding its scope, the chapter also reviews key contractual duties and legal obligations in European legal systems, offering a comparative analysis of informed consent frameworks, patient autonomy, and professional standards across Portugal, Spain, France, Germany, Italy, and the United Kingdom. This broad examination underscores both common principles and distinctive approaches to safeguarding patient rights and defining physicians’ responsibilities across jurisdictions.