In this article we describe characteristics of emergency encounters for patients with a diagnosis of acute cardiac ischemia (ACI) and for patients with chest pain complaints. Data are from the National Hospital Ambulatory Medical Care Survey, which includes abstracts from the medical records of a national probability sample of visits to emergency departments (ED). Analysis was limited to records of patients 25 years of age and older with a diagnosis of either confirmed or suspected acute myocardial infarction (AMI) or unstable angina pectoris and records with a nontraumatic chest pain complaint. There was an estimated annual average of 1.2 million visits to EDs by patients 25 years and over with a diagnosis of ACI in 1995-1996, an average annual rate of 7.2 visits per 1,000 persons. Visit rates varied by patient's age, race, and gender. Chest pain was a complaint in three-fourths of all ACI visits. There were an estimated 4.6 million annual ED visits where in patients aged 25 years and older had complaints of nontraumatic chest pain, an average annual rate of 27.7 visits per 1,000 persons. ACI accounted for 11% of all chest pain visits, but the probability of the chest pain visit having an ACI diagnosis varied by patient's age and race. There remains a large amount of variation in treatment for suspected and confirmed AMI, and for patients presenting with chest pain to EDs.