The present study, using patients with Takayasu's disease (pulseless disease), characterized by segmentally affected arterial lesions and stenotic conditions with a nonspecific inflammatory morbid condition, was designed to assess whether or not a low dose of aspirin can practically exert its preventive effect against the aggregation of platelets that have just passed along a rough-surfaced arterial wall. Twenty Japanese women with Takayasu's disease were selected under the following criteria: A unilateral upper extremity was angiographically confirmed to be affected with the disease, while the contralateral limb was almost normal. Systolic blood pressure on the affected side was almost half that on the nonaffected side. The patients showed neither a positive CRP nor an accentuated ESR. In these patients, mean plasma levels of TXB2 and 3 microM ADP-induced platelet aggregation in blood obtained from the affected side were 156.5 +/- 17.7 pg/ml, and 59.5 +/- 6.0%, respectively, which were significantly high as compared with 104.5 +/- 17.6 and 41.7 +/- 8.8%, respectively, in samples from the nonaffected side. Forty and eighty mg of aspirin per day administered to two randomly composed groups, respectively, showed an improvement in platelet aggregability and TXB2 levels on the nonaffected side. In the affected limbs, though 80 mg/day led to significant decreases in TXB2 levels (108.0 +/- 7.8 pg/ml, p less than 0.05) and platelet aggregability (21.3 +/- 7.6%), the 40-mg regimen showed no significant reductions (134.6 +/- 9.4 pg/ml, 35.6 +/- 17.1%). Plasma levels of 6-keto PGF1 alpha revealed no differences between 40- and 80-mg regimens, or between before and after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)