Background/Aim. The coronary angiography provides information on the anatomical state of the coronary tree, while myocardial perfusion scintigraphy (MPI) facilitates the evaluation of the grade of ischaemia that a particular stenosis produces. The purpose of MPI is to detect the coronary stenosis that provokes the ischaemia and is termed the "culprit lesion". The aim of this study was to evaluate the accuracy of 1-day DypEX 99mTc-tetrofosmin tomography in the identification and localization of culprit lesion in the patients with known coronary artery disease (CAD). Methods. Ninety-one (91) patients with known CAD were studied. In all of them significant coronary narowing (≥ 75% luminal stenosis) was angiographically detected. All the patients were submitted to 2 iv. injections of 99mTc-tetrofosmin, one in a peak of pharmacologic dipyridamole stress protocol with concomitant low level bicycle exercise 50W (DypEX) and the other 3 h after exercise. Quantification of regional tetrofosmin uptake was performed using short-axis myocardial tomogram that was divided on 17-segments for each study. Reversibility scor (RS) ≥ 3 determinated culprit lesion. Two of segments with scor 5 (index of reversibility scor - IRS) in the territory of coronary artery stenoses determinated culprit lesion. Results. A total of 273 vascular territories (4641 segments) were analyzed before percutaneous coronary intervention (PCI). Overall sensivity, specificity, and accuracy using RS ≥ 3 and IRS were 90.1%, 87.1%, 89.4%, with positive predictive value 95.8%, and 94.1%, 93.3%, 94%, with positive predictive value 98%, respectively. Conclusion. RS and IRS significantly improve sensitivity, specificity, and accuracy for determination of culprit lesion in patients undergoing PCI.