Health care costs have been rising steadily in most industrialized countries. These increases are driven primarily by technological advances and, to a lesser degree, by aging of the population. Many factors make it unlikely that market forces alone will limit increases in the costs of health care. These unremitting increases make health care rationing appear both necessary and inevitable.One of the least controversial mechanisms for rationing could be to allow patients to make their own choices as to which kinds of care they would be willing to forgo. This is appealing because it preserves individual freedom of choice regarding health care in a way that other rationing mechanisms often do not. Rationing by patient choice, however, can only happen if patients recognize that resources are limited and need to be conserved, and are willing to forgo marginal benefits.