Echocardiographic measurements of left ventricular end-systolic dimension and fractional shortening obtained in the supine position before and immediately after maximal upright exercise were evaluated in 11 normal volunteers, 35 patients with coronary artery disease and 17 patients without coronary artery disease. The time course of recovery from acute exercise-induced changes in echocardiographic dimensions was analyzed using serial postexercise recordings from normal subjects. An exercise-induced decrease in end-systolic dimension (greater than or equal to 3 mm) and increase in fractional shortening (greater than or equal to 5%) persisted for 3 minutes or longer in the immediate postexercise period in each of the normal volunteers. With these criteria to separate normal from abnormal responses, abnormal responses were observed in 16 (94%) of 17 patients with coronary artery disease and in only 2 (6%) of 35 patients without coronary artery disease. Immediate postexercise echocardiography appears to be a practical and potentially valuable adjunct in the detection of coronary artery disease.