In order to investigate the response of plasma fibrinolytic activity to exercise in patients with ischaemic heart disease, we studied 109 patients with chronic stable angina pectoris. All patients were exercised on the treadmill according to the Bruce protocol. They were subsequently divided into 2 groups according to the results of exercise testing. The first group comprised 47 patients with negative exercise tests and the second group 62 patients with positive exercise tests. The plasma fibrinolytic activity was determined in all patients by the method of euglobulin lysis time before exercise, at peak exercise and 2 hours later. The results were compared with those of a control group which consisted of 30 normal healthy volunteers. In the control group there was a significant increase of plasma fibrinolytic activity (P less than 0.001) at peak exercise, which almost returned to the resting levels at 2 hours. In all patients with angina, resting and peak exercise fibrinolytic activity level was significantly lower than that of the control group (P less than 0.01 and less than 0.001, respectively), although at peak exercise it also increased significantly (P less than 0.001) compared to resting levels and it remained elevated at 2 hours after exercise (P less than 0.001). In patients with negative exercise test, plasma fibrinolytic activity at rest was almost identical to that of the control group, it increased with exercise (P less than 0.001) but to values below those of the control group (P less than 0.01) and although there was a tendency to return to resting levels it remained elevated (P less than 0.01) at 2 hours.(ABSTRACT TRUNCATED AT 250 WORDS)