This study was undertaken to determine the significance of diastolic left ventricular function in 26 normal subjects and in 74 patients with coronary artery disease (CAD). Gated radionuclide left ventriculography in supine position and left anterior oblique projection was performed at rest in both groups considered and during exercise in 11 normal subjects and in 35 patients with CAD. Compared with the normal subjects, the group of patients with CAD showed lower values of global and regional ejection fraction as well as of peak ejection and filling rates. 33 patients with CAD, presenting an ejection fraction greater than 54%, showed similar values of global and regional ejection fraction, compared with the group of normal subjects, while peak filling rate was significantly lower. During exercise peak filling rate significantly increased in normal subjects and in patients with CAD; this increase was constant and similar in the various subgroups considered among patients with CAD. We conclude that peak filling rate represents a more sensitive index than ejection fraction in evaluating left ventricular function in patients with CAD, as shown by the comparison between normal subjects and patients with CAD, who had an ejection fraction greater than 54%.