The most common chronic condition experienced by adults is multimorbidity, the coexistence of multiple chronic diseases or conditions. In patients with coronary disease, for example, it is the sole condition in only 17% of cases.1 Almost 3 in 4 individuals aged 65 years and older have multiple chronic conditions, as do 1 in 4 adults younger than 65 years who receive health care.2 Adults with multiple chronic conditions are the major users of health care services at all adult ages, and account for more than two-thirds of health care spending.2