In coronary patients angina pectoris at rest is usually attended by clear changes in repolarization, and in the absence of such changes clinicians are justifiably reluctant to assert that the constrictive chest pain is due to ischaemia. However, a number of concordant data indicates that in some cases myocardial ischaemia--whether spontaneous or induced by the ergonovine test or by coronary angioplasty--may cause an anginal pain that proceeds without significant alterations in repolarization and indeed, without any changes in ECG tracings. Prior to making a firm diagnosis of this type of angina, several causes of error must be excluded, the main one being that repolarization disorders are labile and may have disappeared whilst the anginal pain persists. But above all, the ischaemic episode that accompanies angina must be documented by haemodynamic, angiographic, scintigraphic or echocardiographic data. The pathogenesis of angina at rest occurring in coronary patients and without changes in per-critical ECG is still imperfectly known and probably complex. The authors review several possible mechanisms: the pain perception threshold may be lowered, the collateral circulation may be highly developed, and the ischaemic episode may be so discreet and/or controlled by treatment, or so evenly distributed between two opposite territories that no electric gradient is generated.