As in most other nuclear medicine facilities, tomographic myocardial imaging was started here with the patients in the supine position. However, previous planar imaging experience indicated a high number of false-positive results using the supine position for left lateral views of the myocardium. Evaluating the accuracy of supine position SPECT imaging was considered necessary. In 1991, 228 myocardial imaging procedures were performed during a period of 3 months. Coronary arteriography followed within 3 months in 67 of these patients, permitting evaluation of the accuracy of the imaging procedure interpretations. These correlations revealed the accuracy of myocardial imaging to be only 73%. This was caused mainly by a rather large number of false-positive results (24%) occurring mostly in the inferior-posterior wall. A similar comparison was performed in 1992 after a change to prone position for routine tomographic myocardial imaging with 63 of 295 patients undergoing coronary arteriography. These data revealed an increase in the overall accuracy to 81% and a decrease in the false-positive results to 16%. The improvements were almost entirely in the inferior-posterior regions with no significant change in the false-positive results in the anterior wall. These findings provide convincing evidence that the prone position should be selected for tomographic myocardial imaging.