This study updates prevalence estimates of single chronic conditions and multiple chronic conditions (MCC) among noninstitutionalized, civilian US adults using data from the 2012 National Health Interview Survey (NHIS). Approximately half (49.8%, 117 million) of US adults had at least one of 10 chronic conditions, including hypertension, coronary heart disease, stroke, diabetes, cancer, arthritis, hepatitis, weak or failing kidneys, asthma, and COPD. About 25.5% of US adults had MCC, with 1 in 4 adults having MCC. The prevalence of MCC increased from 26% in 2010 to 25.5% in 2012, showing no significant decrease. MCC prevalence varied by age, sex, race/ethnicity, and health insurance coverage. Women were more likely than men to have MCC, and prevalence was higher among non-Hispanic white, non-Hispanic black, and non-Hispanic adults of other races compared to non-Hispanic Asian and Hispanic adults. The percentage of adults with MCC increased with age. Adults with public coverage had higher MCC prevalence than those with private or other coverage. The study highlights the growing public health concern of MCC and the need for better research, data, and surveillance to address this issue. The NHIS estimates are likely conservative as they include only 10 of 20 chronic conditions standardized for consistent measurement. Mental health conditions were not included in the study. The findings emphasize the importance of improving healthcare and public health systems, enhancing self-care management, and providing better tools for healthcare providers to address MCC. Further research is needed to monitor MCC more frequently and improve prevention and intervention strategies.This study updates prevalence estimates of single chronic conditions and multiple chronic conditions (MCC) among noninstitutionalized, civilian US adults using data from the 2012 National Health Interview Survey (NHIS). Approximately half (49.8%, 117 million) of US adults had at least one of 10 chronic conditions, including hypertension, coronary heart disease, stroke, diabetes, cancer, arthritis, hepatitis, weak or failing kidneys, asthma, and COPD. About 25.5% of US adults had MCC, with 1 in 4 adults having MCC. The prevalence of MCC increased from 26% in 2010 to 25.5% in 2012, showing no significant decrease. MCC prevalence varied by age, sex, race/ethnicity, and health insurance coverage. Women were more likely than men to have MCC, and prevalence was higher among non-Hispanic white, non-Hispanic black, and non-Hispanic adults of other races compared to non-Hispanic Asian and Hispanic adults. The percentage of adults with MCC increased with age. Adults with public coverage had higher MCC prevalence than those with private or other coverage. The study highlights the growing public health concern of MCC and the need for better research, data, and surveillance to address this issue. The NHIS estimates are likely conservative as they include only 10 of 20 chronic conditions standardized for consistent measurement. Mental health conditions were not included in the study. The findings emphasize the importance of improving healthcare and public health systems, enhancing self-care management, and providing better tools for healthcare providers to address MCC. Further research is needed to monitor MCC more frequently and improve prevention and intervention strategies.