In the United States, 125 million people are living with chronic illness, disability, or functional limitation.1 The nature of modern medicine requires that these patients receive assistance from a number of different care provi ders. Between 2000 and 2002, the typical Medicare beneficiary saw a median of two primary care physicians and five specialists each year, in addition to accessing diagnostic, pharmacy, and other services. Patients with several chronic conditions may visit up to 16 physicians in a year.2 Care among multiple providers must be coordinated to avoid wasteful duplication of diagnostic testing, perilous polypharmacy, and confusion about conflicting care plans.