As health care has become of great importance to both individual citizens and to society, it has become more important to understand medicine's relationship to the society it serves in order to have a basis for meaningful dialogue. During the past decade, individuals in the medical, legal, social sciences, and health policy fields have suggested that professionalism serves as the basis of medicine's relationship with society, and many have termed this relationship a social contract. However, the concept of medicine's social contract remains vague, and the implications of its existence have not been fully explored. This paper endorses the use of the term social contract, examines the origin of the concept and its relationship to professionalism, traces its evolution and application to medicine, describes the expectations of the various parties to the contract, and explores some of the implications of its use.