Medicare is a critical piece of our current health care system. In fact, many reform proposals treat Medicare's basic structure as "untouchable," suggesting only modest changes in the program while significantly altering many other aspects of the health care system. Nevertheless, it would be a mistake to view Medicare as irrelevant to the reform process. First, Medicare's experience offers important perspectives—both positive and negative—for reform. Moreover, changes elsewhere in the system will have an effect on the Medicare program; it is not possible to enact reforms that dramatically change the delivery of care without also affecting Medicare, even if no formal provisions of the program are altered. And the one area in which most proposals would affect Medicare—cuts in payments to providers to help fund other expansions—may place the program at risk.