Sixty patients without organic heart disease presenting with chest pain suggestive of angina pectoris and angiographically normal coronary arteries underwent clinical, hemodynamic and metabolic investigation. The study of myocardial lactate metabolism during atrial pacing (168 +/- 14 bpm) allowed identification of two groups: --40 patients with a normal coefficient of lactate extraction (K greater than or equal to 9 per cent); --20 patients with a pathologically low coefficient of lactate extraction (K less than 9 per cent) reflecting myocardial ischemia. In the first group, chest pain was often atypical (75 per cent of cases). Hemodynamic investigation showed minor abnormalities of the left ventricle in 48 per cent of cases. The diagnosis of angina was rejected in these patients. In the second group, the majority of patients developed chest pain (85 per cent of cases) at the maximal heart rate with significant ST depression (80 per cent of cases). The chest pain was typical of angina pectoris in 50 per cent of cases. Hemodynamic and angiographic investigation of the left ventricle was completely normal in nearly all cases. Only these patients with clinical, electrocardiographic and metabolic signs of myocardial ischemia can be considered as having angina with normal coronary arteries. Although studies of myocardial lactate metabolism and other signs of myocardial ischemia distinguish clearly between these two groups of patients, the coronary hemodynamics were similar. Resting coronary flow, its increase for the same myocardial oxygen demands and coronary resistances were comparable in both groups, and not significantly different from the values obtained in a control group of patients without coronary artery disease or chest pain. These results confirm that about 30 per cent of patients investigated for chest pain suggestive of angina pectoris who have angiographically normal coronary arteries, develop signs of myocardial ischemia during atrial pacing. The physiopathological explanation remains unclear as coronary hemodynamics have been found to be normal.