The growing use of unsubstantiated complementary and alternative medicine therapies by people in the United States1 along with its increasing coverage by third party payers2 encouraged Congress to create the National Center for Complementary and Alternative Medicine (NCCAM) at the National Institutes of Health. The centre's mission is “to explore complementary and alternative healing practices in the context of rigorous science; to educate and training CAM researchers; and to disseminate authoritative information to the public and professionals.”3 To complete this mission, NCCAM supports publicly relevant and scientifically rigorous research to identify those complementary and alternative medicine practices that are safe and effective.

The centre's resources, although generous ($68.3m (£46m) for fiscal year 2000), are not sufficient to study all complementary and alternative medicine practices. NCCAM therefore developed criteria to help prioritise the many possible research opportunities (box). As part of the evaluation process, NCCAM seeks advice from its national advisory council, complementary and alternative medicine and conventional clinicians, members of the scientific research community, the public, sister federal agencies, and other stakeholders.