The purpose of this study was to discover whether the passage of contrast medium through the myocardium can be visualized by digital subtraction angiocardiography and whether myocardial perfusion can be determined qualitatively from the difference images. Cineangiograms (duration 20 s) were obtained during routine coronary angiography and analyzed by means of a computerized image processing system. The results show that the passage of contrast medium through the coronary artery system, myocardium and coronary veins can be visualized. In 10 patients myocardial perfusion at rest was classified qualitatively into four categories (well perfused, slightly reduced perfusion, markedly reduced perfusion and perfusion defect) from local contrast intensity and the time dependent wash-in phase of the contrast medium. Intra- and interobserver comparison of the qualitative estimation of myocardial perfusion showed a close correlation (p less than 0.001 to p less than 0.0001). In the same 10 patients myocardial perfusion at rest was evaluated from Tl-201 scintiscans by two independent observers. A comparison between the qualitative classification of local myocardial perfusion assessed by both methods revealed a close correlation (p +/- 0.049). These results indicate that myocardial perfusion at rest can be visualized by digital image processing and evaluated qualitatively from cineangiograms.