To determine the effect of aging on left ventricular filling, mitral valve flow was evaluated with real-time (color flow) and conventional pulsed Doppler echocardiography in 32 subjects, aged 24 to 68 years, who had no evidence of cardiovascular disease. The diameter of mitral valve flow was measured in early and late diastole in the apical 4-chamber view. Transmitral velocities were measured in early and late diastole with pulsed Doppler echocardiography. The early flow diameter was significantly smaller in patients older than 50 than in those aged 20 to 29 years (p less than 0.05), while atrial flow diameter was significantly larger in patients older than 50 than in those aged 20 to 29 years (p less than 0.05). The ratio of early flow diameter to atrial flow diameter was 1.85 +/- 0.33 in patients 20 to 29 years old and 1.17 +/- 0.28 in those older than 50 (p less than 0.001). The ratio of early to atrial diastolic velocities was 1.98 +/- 0.53 in the younger patients and 1.07 +/- 0.41 in those older than 50 years (p less than 0.001). The ratio of early flow diameter to atrial flow diameter decreased significantly with aging, and this decrease had a negative correlation with aging (r = -0.64). Qualitatively, in these normal subjects, early diastolic flow filled the ventricle centrally, while with atrial contraction, flow entered the ventricle toward the posterolateral wall and was associated with flow moving toward the aortic valve along the ventricular septum.(ABSTRACT TRUNCATED AT 250 WORDS)