For measurement of ventricular performance, ejection fraction (EF) has gained wide acceptance. But EF is influenced not only by changes in muscle function but also by changes in cardiac loading conditions. In case of valvular geart disease which is variable in loading conditions, EF cannot be reliable as an index of myocardial contractility. The end systolic pressure (ESP)-end systolic volume (ESV) relation, howver, is known to represent myocardial contractility, independent of changes in loading conditions. Similar results can be obtained by using peak-systolic presure (PSP) instead of ESP. To evaluate the utility of the peak systolic pressure-end systolic volume index (PSP- ESVI) relation as an index of myocardial function, we measured PSP & ESVI in 19 partents with coronary artery disease before (PSP& ESVI) and after (PSP & ESVI) sublingeal administration of nitroglycerin, PSP was measured with standard mercury sphygmomanometer during gated blood pool scintigraphic study. ESVI was measured by count derived method after attenuation correction. PSP & ESVI measurement was started when the fall of PSP was greater than 5 mmHg after 7-14 minutes post- administration of nitroglycerin. Mean values ( + - S.D.) of PSP & ESVI was 124.9( + - 20.7) mmHg 59.4(+- 39.9) ml/M2. Mean values ( + - S.D) of PSP & ESVI was 113.2(+ - 19.9)mmHg & 37.5(+ - 26.1)ml/M2. There was a significant difference between mean values of PSP & PSP (p<0.01), and mean values of ESVI & ESVI (p<0.01)PSP- PSP/ESVI-ESVI, PSP/ESVI and EF were in the range of 0.14-5.19 mmHg/ml/M2, 0.67-7.68 mmHg/ml/M2 and 10.8%-74.5% respectively. PSP-PSP/ESVI-ESVI and EF showed exponetial correlation (r=0.85, P<0.01). The correlation coefficient between PSP/ESVI and EF was 0.73(p<0.01). With the above results, we suggest that PSP1-PSP2/ESVI1-ESVI2 and PSP1/ESV1 can be usde as an index of myocardial function.