The differential diagnosis of ST-segment elevation includes four major processes: ST-segment elevation myocardial infarction (STEMI); early repolarization; pericarditis; and ST elevation secondary to an abnormality of the QRS complex (left bundle branch block, left ventricular hypertrophy, or preexcitation). Other processes that may be associated with ST elevation include hyperkalemia, pulmonary embolism, and Brugada syndrome. The clinical setting and specific electrocardiographic criteria often allow identification of the cause. This article reviews ST-T and QRS configurations specific to each diagnosis.