Care more particularly for the individual patient than for the especial features of the disease. William Osler 1 One of the most daunting challenges confronting the health care system is how to prevent and manage multiple chronic conditions (MCC) effectively and efficiently. MCC are commonly defined as the co-occurrence of two or more chronic physical or mental health conditions. Some use the term multimorbidity as synonymous with MCC, while others define MCC as including additional factors that contribute to the burden of illness, including disease severity, functional impairments and disabilities, syndromes such as frailty, and sometimes social factors such as homelessness. 2 Regardless of definition, MCC are common, costly, and place a high burden on individuals, their caregivers, clinicians, health care teams, and health systems alike. Our fragmented, disease-focused health care system is ill-designed to meet the needs of this growing population.Although prevalence varies with definition, 3 MCC is the most common chronic condition seen in clinical practice. One in three American adults, four in five Medicare beneficiaries, and a growing number of children have MCC. People living with MCC account for a disproportionate share of health care utilization and costs, 64% of all clinician visits, 70% of all inpatient stays, 83% of all prescriptions, 71% of all health care spending, and 93% of Medicare spending. Almost half have functional impairments. Nearly all readmissions among Medicare beneficiaries occur among those with MCC. 4 The prevalence of MCC will grow with our aging population. The need to