Even without comprehensive health care reform legislation, the US health care system is undergoing significant changes. Probably the most important change is the expansion of managed care with significant price competition. One of the major concerns about this change is the effect of managed care on the physician-patient relationship. To provide a normative standard for evaluating the effect of changes, we need an ideal conception of the physician-patient relationship. This ideal can be summarized by six C's: choice, competence, communication, compassion, continuity, and (no) conflict of interest. For the 37 million uninsured Americans there is little chance of realizing the ideal physician-patient relationship, since they lack the choice of practice setting and physician, receive care in a rushed atmosphere that undermines communication and compassion, and have no continuity of care. While many insured Americans may believe they have an ideal physician-patient relationship, the relationship is threatened by lack of a regular assessment of competence, by financial incentives that undermine good communication, and by the persistence of conflict of interest. The shift to managed care may improve the choice of practice settings, especially in sections of the country that currently lack managed care; increase choice of preventive services; make quality assessments more routine; and improve communication by making greater use of primary care physicians and nonphysician providers. However, the expansion of managed care and the imposition of significant cost control have the potential to undermine all aspects of the ideal physician-patient relationship. Choice could be restricted by employers and by managed care selection of physicians; poor quality indicators could undermine assessments of competence; conductivity requirements could eliminate time necessary for communication; changing from one to another managed care plan to secure the lowest costs could produce significant disruption in continuity of care; and use of salary schemes that reward physicians for not using medical services could increase conflict of interest.