Is medical commerce a recent phenomenon? Does it distort the patientphysician relationship? Are investor-owned firms the main source of medical commercialism? 1 I contend that medicine has generally been commerce in the United States, that medical commerce is a problem when it creates or worsens physicians' conflicts of interest, and that these conflicts thrive in nonprofit organizations as well as in investor-owned firms. I provide a historical sketch to show that physician entrepreneurialism, rather than commerce generally, is the main source of physicians' conflicts of interest. Physicians have a conflict of interest when they have an obligation to act in their patients' interest and have incentives to act in their own interest, also the interest of other parties or they perform roles that prompt them to act in the interest of third parties. 2 Conflicts of interest compromise physicians' loyalty to patients or their independent judgment in acting on behalf of their patients and thereby increase the risk that they may not fulfill their obligations. To reduce this risk, public policy and professional ethics sometimes restrict engaging in activities that create conflicts of interest or regulates them. Self-employed physicians are entrepreneurs in that they earn profits and bear the risk of loss from their practice. 3 They sell medical services, tests, drugs, medical devices, and may own or invest in hospitals or other medical facilities. They have conflicts of interest arising from incentive to manage their practice and to advise, prescribe, refer, and make clinical choices that promote their income, even at the patient's expense. 4 A Continuum of Entrepreneurial Opportunities in Private Medical Practice The degree of entrepreneurial opportunities physicians have depends on how private practice is organized. Consider solo primary care practitioners, paid fee-for-service, who examine patients, diagnose problems, prescribe medicine, provide simple treatment, and refer patients to specialists. Such practitioners can increase their income by raising fees or providing more services, either by treating more patients or by performing more services for existing patients. If solo practitioners have more time than patients, pursuit of income might lead them to perform unnecessary services. Thanks are due to Jerome P. Kassirer, Albert R. Jonsen, and Joseph Fins for helpful comments on a draft. The history and themes herein are further developed in a book I am now writing, titled Medical Profession, Market and State in France, the United States and Japan.