Forty-two patients who underwent aorto-coronary bypass surgery were examined with intra-aortic digital subtraction angiography (IADSA) to detect abnormalities of myocardial blood perfusion. Tl-201 myocardial imaging and cardiac X-ray CT were performed nearly simultaneously about one month postoperatively. Cardiac imaging using IADSA was performed at a rate of 30 frames/sec with matrix size of 512 x 256. Time density curves of each pixel in the region of the myocardium of the left ventricle were post-processed to obtain functional images. The maximal concentration (Cmax), integration of the time-density curve (Cinteg), mean transit time (MTT), Cmax/MTT and Cinteg/MTT were computed for each pixel. Cmax and Cinteg are parameters related to the volume of the coronary vascular bed. Cmax/MTT and Cinteg/MTT are parameters related to the regional myocardial blood flow. These functional images showed hypoperfusion areas in 35 of 37 ischemic segments confirmed by wall motion in digital subtraction left ventriculography, Tl-201 myocardial imaging and ECG. Normal perfusion areas of the functional images were observed in 18 of 54 infarcted segments. These results show the complexities of myocardial perfusion in old myocardial infarction.