Acute coronary syndrome is a serious condition that requires urgent assessment and management. This article outlines the nature of the condition, and discusses its underlying pathophysiology. It discusses three types of acute coronary syndrome: unstable angina, ST elevation myocardial infarction and non-ST elevation myocardial infarction. Research and guidelines are used to guide the reader through approaches to initial nursing assessment and the immediate management of patients with suspected acute coronary syndrome.