This study determined whether the diagnosis of myocardial viability could be established on the basis of the contractile reserve during low level exercise with an ergometer using echocardiography. The study involved 22 patients with transmural old myocardial infarction who underwent exercise echocardiography, followed by coronary intervention after a mean 4 days. Exercise echocardiography was started from 50 W and stepped up by 25 W every 3 min up to a maximum of 150 W. Low level exercise was administered for 1 to 2 min at 50 W. A 16-segment model was used for the left ventricular wall motion, which was evaluated by five-grade scoring, ranging from normokinesis to dyskinesis. If patients showed improvement by one point or more in the score for segments of dyskinesis, akinesis, or severe hypokinesis on the exercise echocardiography, they were considered to have positive viability. The golden standard for the diagnosis of myocardial viability was that wall motion abnormalities before exercise echocardiography should be improved by one point or more after coronary intervention. Before exercise echocardiography, there were 152 segments showing wall motion abnormalities assessed as severe hypokinesis or more. After coronary intervention, improvement of the wall motion by one grade or more was found in 2 of the 18 segments (11%) for dyskinesis, in 38 of the 96 segments (40%) for akinesis, and in 22 of the 38 segments (58%) for severe hypokinesis; improvement for the segments of severe hypokinesis was significantly better than those for dyskinesis and akinesis. Out of 19 segments with akinesis before exercise echocardiography in which wall motion was improved during low level exercise, 16 segments (84%) showed improvement in wall motion after coronary intervention. Out of 77 segments with akinesis before exercise echocardiography in which no change or worsening was seen during low level exercise, 22 segments (29%) showed improved wall motion after coronary intervention. There were 38 segments with severe hypokinesis before exercise echocardiography; out of 12 segments in which wall motion was improved during low level exercise, 7 segments (58%) showed improved wall motion after coronary intervention. Out of 26 segments with severe hypokinesis before exercise echocardiography in which no change or worsening was seen during low level exercise, 11 segments (42%) showed improved wall motion after coronary intervention. Wall motion was improved after coronary intervention in 20 of 25 segments (80%) that showed the biphasic response, in 4 of 7 segments (57%) that showed improvement, in 14 of 43 segments (33%) that showed worsening, in 24 of 77 segments (31%) for no change; the biphasic response showed a significantly higher improvement compared to worsening or no change. If segments in which wall motion was improved during low level exercise are regarded as positive viability segments, occurrences of the sensitivity, specificity and diagnostic accuracy of myocardial viability were 50%, 84%, and 71%, respectively.