Coronary angiography is the "gold-standard" of the diagnostic approach in the patients with suspected coronary artery disease. Although it can be safely and easily performed in a modern cardiac catheterization laboratory, it is nevertheless responsible for a certain degree of morbidity and mortality related to the invasive nature of the procedure, and especially to the use of an iodinated contrast agent. Unlike certain functional tests, the results of coronary angiography are extremely "operator-dependent", which probably constitutes the most difficult limiting element to overcome in practice. Prognostic elements provided by coronary angiography (site and extent of lesions) must also be compared with the results of the reference functional test, Thallium 201 stress myocardial scintigraphy.