To evaluate left ventricular (LV) reserve, we developed a method of dynamic exercise echocardiography (DEE). Forty-six healthy persons and 47 cardiac patients performed bicycle ergometer exercise in the supine position. A special table was used on which the subjects could be firmly attached at shoulder level to prevent bodily movements which might disturb the recordings. In 83% of the subjects in whom a clear echocardiogram was obtained at rest, a clear echocardiogram was also obtained during dynamic exercise. During exercise, cardiac output estimated from the echocardiogram and that from the dye-dilution method showed an excellent correlation. The changes of the mean velocity of LV circumferential shortening during exercise permitted discrimination between older and younger healthy men, and also between healthy subjects and those with either mild or severe LV dysfunction. We conclude that DEE is useful for evaluating LV reserve.