In this study, transmitral flow velocity during the diastolic period was noninvasively measured to assess diastolic behavior of the left ventricle by pulsed Doppler flowmetry combined with electronic beam sector-scanning echo-cardiography. The velocity pattern was found to have 2 wave components: one appears in the early diastolic rapid filling phase (R wave) and the other in the late diastolic phase. The peak of the early diastolic inflow velocity (peak EFV), the deceleration rate of the R wave (DO, and the peak of the late diastolic inflow velocity (peak LFV) were compared in healthy subjects as the control, patients with hypertension, hypertrophic cardiomyopathy and definite old myocardial infarction. Normal peak EFV and DC, 61.3 ± 6.7 cm/sec and 355 ± 67 cm/sec², respectively, were markedly reduced in patients with hypertension (50.0 ± 10.0 cm/sec and 265 ± 75 cm/sec²), hypertrophic cardiomyopathy (48.8 ± 10.7 cm/sec and 205 ± 78 cm/sec²), and myocardial infarction (46.1 ± 12.0 cm/sec and 240 84 cm/sec²). Among all disease groups the DC was most significantly reduced in the hypertrophic cardiomyopathy group. Normal peak LFV, 39.9 11.0 cm/sec, was significantly increased in patients with hypertension (54.3 10.7 cm/sec) and myocardial infarction (50.0 11.O cm/sec), but not in patients with hypertrophic cardiomyopathy (42.0 8.4 cm/sec). The ratio peak LFV/peak EFV was significantly greater in all disease groups than in the normal group. These findings indicate that impaired early diastolic filling in all disease groups was compensated by enhanced atrial contraction in patients with hypertension and myocardial infarction, and by prolonged rapid filling in patients with hypertrophic cardiomyopathy. Left ventricular wall thickness was better correlated with DC in patients with hypertension (r = -0.76, p < 0.01) than in patients in the other groups, which indicates that the left ventricular wall thickenning is a more important factor in determining diastolic behavior of the ventricle in hypertension than in hypertrophic cardiomyopathy and myocardial infarction. Thus, the pulsed Doppler technique was proved to be useful in assessing ventricular diastolic events non-invasively.