On the basis of a synthesis of the scientific literature and advice from its public health partners, the CDC has defined HRQOL as “an individ­ual’s or group’s perceived physical and mental health over time.” The core Healthy Days measures assess a person’s per­ceived sense of well-being through four questions on: 1) self-rated health, 2) number of recent days when physical health was not good, 3) number of recent days when mental health was not good, and 4) number of recent activity limitation days because of poor physical or men­tal health (see BRFSS “Health Status” questions @http://www.cdc.gov/nccdphp/brfss/). (author abstract)