It has been observed in small numbers of patients that, unlike patients with chronic stable ischemia, patients with unstable angina or non-Q-wave myocardial infarction frequently have a thrombus in a major coronary artery. Initial conventional therapy for unstable angina consists of bed rest, oxygen, nitrates, beta-blockers, calcium antagonists, and aspirin. The use of heparin is widespread but controversial. In many tertiary care hospitals, angiography followed by PTCA is frequently performed, whereas in community hospitals patients are often managed without angiography.