The future of social medicine is based on 150 years of history and the rapidly evolving context within which medicine functions in modern societies. There are two views of social medicine. One is based on the vision of Guerin and, particularly, Virchow 150 years ago that: "Doctors are the natural advocates of the poor, and social problems are largely within their jurisdiction." The New York Academy of Medicine's Institute on Social Medicine 50 years ago reflected this broad view. Medicine, however, enamored of the biomedical paradigm and the advances in knowledge through biomedical research, largely abandoned this broad perspective, even as the knowledge about the social, behavioral, and environmental determinants of health was advancing rapidly. A second view of social medicine, and one that has influenced many in the past 30 years, was defined by McKeown and Lowe: "Social medicine is concerned with a body of knowledge and methods of obtaining knowledge appropriate to a discipline. This discipline may be said to comprise (a) epidemiology, and (b) the study of the medical needs of society, or in the contemporary short hand medical care." Social medicine, in my view, includes not only the definition of McKeown and Lowe, but the broader context within which medicine fits in society. The context is changing. The social contract as defined by Bismarck and Beveridge has to be redefined. Just as the New York Academy of Medicine provided the vision of social medicine 50 years ago, the Academy has given us a new vision with the publication of Medicine and Public Health: the Power of Collaboration in 1997. Authored by Dr. Roz Lasker, director of the Academy's Division of Public Health, the book identifies the key changes required by medicine and public health to advance the goals of medicine and public health for the benefit of both individual patients and the population as a whole. The book points the way for the future of social medicine by identifying not only what needs to be done, but also how to do it.