Respect for patient privacy and confidentiality is an ancient and a contemporary professional responsibility of physicians. Carrying out this responsibility may be more challenging and more important in the emergency department than in many other clinical settings. Part I of this 2-part article outlines the basic concepts of privacy and confidentiality, reviews the moral and legal foundations and limits of these concepts, and highlights the new federal privacy regulations implemented under the Health Insurance Portability and Accountability Act of 1996. Part II of the article examines specific privacy and confidentiality issues commonly encountered in the ED.