Diastolic left ventricular (LV) properties were studied at rest and during spontaneous angina pectoris during cardiac catheterizatlon in 10 patients with severe coronary artery disease. During spontaneous angina there was a significant increase in LV filling pressures through diastole. The right ventricular end-diastolic pressure was measured at rest and during spontaneous angina in 7 of 10 patients and showed an increase from 7 ± 3 to 10 ± 4 mm Hg (mean ± SD) (p < 0.02). The T index (a measure of LV isovolumic relaxation) at rest was 51 ± 17 ms and increased during angina to 58 ± 12 ms (p < 0.01), indicating an early diastolic relaxation dysfunction. Frame-by-frame LV volumes and corresponding pressures were analyzed from 3 consecutive beats in 5 of 10 patients. In 4 of these 5, the pressurevolume loop shifted upward and slightly to the right during angina. There was a significant increase in the rate of filling during mid-diastole with angina. Left atrial stroke work index increased by 35% during angina, suggesting an increased work load on the left atrium to maintain late diastolic filling.