Patients with atherosclerotic disease of the lower limbs are at high risk of thrombotic events not only in the peripheral circulation, but also in the coronary and cerebral arteries. Ticlopidine, a potent inhibitor of platelet aggregation, can reduce the incidence of arterial thrombosis in patients suffering from intermittent claudication, as shown by a meta-analysis performed in 1987. In order to confirm these findings, we undertook a randomized, stratified, placebo-controlled, double-blind multicentre trial in Argentina in two parallel groups of patients suffering from intermittent claudication. Twenty-one clinical centres participated in the trial and 615 patients were enrolled. Patients were eligible if they had presented obstructive arterial disease of the upper part of the lower limb (popliteal or above) for at least 12 months, confirmed by either angiography or Doppler studies, and intermittent claudication (stage II) assessed by treadmill testing. Non insulin treated diabetic patients were eligible if they fulfilled the other inclusion criteria and two strata, diabetic and non diabetic, were established. Patients enrolled were treated with either ticlopidine (500 mg/day) or placebo for 24 weeks. In this paper, we report the design and organization of the study and the baseline characteristics of the patient population at inclusion.(ABSTRACT TRUNCATED AT 250 WORDS)