Paradoxical motion of the posterior left ventricular wall in patients in the upright but not in the supine position was demonstrated in a high percentage of normal volunteers. There was no significant difference in age, body surface area, heart rate, and blood pressure between the groups, with or without paradoxical motion. This echocardiographic finding probably represents a physiologic phenomenon and should be taken into consideration during the interpretation of upright exercise echocardiograms.