Coronary angiography is still the first choice method for the diagnosis of coronary artery disease in patients with dilated cardiomyopathy. The diagnosis of coronary artery disease is, in its turn, essential as patients with associated coronary artery disease have a worse prognosis, compared to patients with idiopathic dilated cardiomyopathy, and, more importantly, coronary revascularization may significantly improve left ventricular function, clinical symptoms and prognosis, when performed in the presence of a significant amount of viable myocardium. The favorable effects on the left ventricular function are greater when a contractile reserve is shown. However, revascularization of viable myocardium may have other beneficial effects like a reduction in left ventricular remodeling and in the incidence of recurrent ischemic events and malignant arrhythmias. The detection of viable myocardium should, however, be preceded by the detection of coronary artery disease through coronary angiography. The clinical history and the results of the non-invasive evaluation, with the possible exception of coronary calcium detection by electron beam computed tomography, do not, in fact, allow the diagnosis of coronary artery disease. Coronary angiography is thus indicated in all the patients with suspected coronary artery disease (e.g. males > 35 years, with coronary risk factors, a history of chest pain and/or regional wall motion abnormalities and/or perfusion defects at stress scintigraphy) in whom the age and general conditions warrant a coronary revascularization procedure. Coronary angiography is also indicated in all the patients who are candidates to heart transplantation or whose symptoms are secondary to a mechanical complication of myocardial infarction.