The study aim was to assess whether post-ejection thickening (PT) is an useful marker of viable myocardium in patients with chronic coronary artery disease. Twenty-three patients with critical coronary stenoses were submitted to dobutamine and dipyridamole stress-echocardiographies and dipyridamole-early-redistribution 201Tl SPECT within 15 days from coronary arteriography. They were selected for the presence of PT in segments that could be optimally studied by M-mode echocardiography and were hypo-akinetic in basal conditions. PT (occurring between end-ejection and mitral valve opening) was found in 58% of dysfunctional, critically perfused regions. Ninety-eight percent of the regions with PT and 6% of those without PT improved during low-dose dobutamine stress-echocardiography. Segments with PT had, respectively, higher and lower SPECT early-redistribution thallium activity than dysfunctional segments without PT and normokinetic regions. Therefore, regions with PT were viable and had a moderate decrease in coronary perfusion. Akinetic segments without PT did not show any inotropic reserve. After revascularization almost all the segments with PT improved. In conclusion, PT is a pattern of myocardial contraction easily detected by M-mode echocardiography in the clinical setting. If the results of this study are further confirmed, PT may become a sign for the recognition of myocardial viability.