Myocardial relaxation at the diastolic phase was not evaluated by multi-gated myocardial SPECT, although myocardial contraction at the systolic phase was studied by percent wall thickening and Bull's eye methods. We make out a myocardial volume curve and report to evaluate the myocardial relaxation using multi-gated myocardial SPECT. The study population consisted of 3 normal human subjects (3 male, 32-37 years old), 10 idiopathic cardiomyopathy, 10 coronary artery disease and 1 hypertensive heart disease combined with aortic regurgitation. All cases were injected 555 MBq of 99mTc-tetrofosmin (Amersham Healthcare Corporation) intravenously at rest. A triple detector gamma-camera (GCA-9300A, Toshiba Medical, Japan) and a data processing computer (GMS-5500A, Toshiba Medical, Japan) were used in this study. A cardiac cycle (R-R interval) was divided by 16 frames (50-80 msec per 1 frame). Eight myocardial volume curves were calculated at the anterior wall, apex and inferior wall of the vertical long axis view and were calculated at the septal wall, apex and lateral wall of the horizontal long axis view, respectively. The patterns of the myocardial volume curves were classified into 5 patterns (Normal pattern (N), Delayed Contraction pattern (DC), Delayed Relaxation pattern (DR), Mixed pattern (M) and Normal pattern with Decreased amplitude (ND)). Myocardial uptake was evaluated visually of grading into severe hypertrophy (5), hypertrophy (4), normal (3), mild hypoperfusion (2), hypoperfusion (1) and perfusion defect (0). We compared patterns of the myocardial volume curves to myocardial uptake in the same segments. It was possible to detect myocardial edge of the total 16 frames with 50-60% threshold in the normal volunteer and in patients with hypertrophic cardiomyopathy and to make a myocardial volume curve. The region of the severe myocardial perfusion defect could be detected with 20% threshold in patients with old myocardial infarction. In comparison with myocardial volume curves and myocardial uptake, 74.6% in the N pattern had a normal uptake (3), 66.7% in the ND pattern had a normal uptake (3), 61.5% in the DC pattern had a hypoperfusion segment (0, 1 or fill-in to normal uptake), 44.4% in the DR pattern had a hypertrophic segment (4, 5 or fill-in to increased uptake). The pattern of myocardial volume curve indicates myocardial contractility and relaxation in each myocardial segment.