Mechanical complications of acute myocardial infarction include papillary muscle rupture with severe mitral regurgitation, ventricular septal rupture with acute ventricular septal defect, acute and subacute free-wall rupture, and hemodynamically significant right ventricular infarction. Although such complications are infrequent, their importance is underscored because of the potential ability to correct them with early diagnosis and appropriate treatment. The diagnosis necessitates a high degree of suspicion based on clinical clues and rapid diagnostic testing. Beside two-dimensional echocardiography, sometimes with transesophageal echocardiography, is most commonly used to diagnose or exclude these complications. Patients suspected of having a mechanical complication of myocardial infarction should be urgently transferred to a medical center experienced in the management of these problems. For deteriorating patients without identifiable mechanical complications, coronary angiography and reperfusion with direct angioplasty should be considered.