The objective of this research was to update earlier estimates of prevalence rates of single chronic conditions and multiple (>2) chronic conditions (MCC) among the noninstitutionalized, civilian US adult population. Data from the 2012 National Health Interview Survey (NHIS) were used to generate estimates of MCC for US adults and by select demographic characteristics. Approximately half (117 million) of US adults have at least one of the 10 chronic conditions examined (ie, hypertension, coronary heart disease, stroke, diabetes, cancer, arthritis, hepatitis, weak or failing kidneys, current asthma, or chronic obstructive pulmonary disease [COPD]). Furthermore, 1 in 4 adults has MCC.