Heart disease is the leading cause of death in the United States (1). Heart attacks (also known as myocardial infarctions) occur when a portion of the heart muscle does not receive adequate blood flow, and they are major contributors to heart disease, with an estimated 750,000 occurring annually (2). Early intervention is critical for preventing mortality in the event of a heart attack (3). Identification of heart attack signs and symptoms by victims or bystanders, and taking immediate action by calling emergency services (9-1-1), are crucial to ensure timely receipt of emergency care and thereby improve the chance for survival (4). A recent report using National Health Interview Survey (NHIS) data from 2014 found that 47.2% of U.S. adults could state all five common heart attack symptoms (jaw, neck, or back discomfort; weakness or lightheadedness; chest discomfort; arm or shoulder discomfort; and shortness of breath) and knew to call 9-1-1 if someone had a heart attack (5). To assess changes in awareness and response to an apparent heart attack, CDC analyzed data from NHIS to report awareness of heart attack symptoms and calling 9-1-1 among U.S. adults in 2008, 2014, and 2017. The adjusted percentage of persons who knew all five common heart attack symptoms increased from 39.6% in 2008 to 50.0% in 2014 and to 50.2% in 2017. The adjusted percentage of adults who knew to call 9-1-1 if someone was having a heart attack increased from 91.8% in 2008 to 93.4% in 2014 and to 94.9% in 2017. Persistent disparities in awareness of heart attack symptoms were observed by demographic characteristics and cardiovascular risk group. Public health awareness initiatives and systematic integration of appropriate awareness and action in response to a perceived heart attack should be expanded across the health system continuum of care.