Platelet aggregation inhibitors are used in numerous clinical situations on the basis of claims that platelets are involved. As a result of controlled clinical trials, some of these situations have become formal indications for some of these drugs. The situations in which platelet aggregation inhibitors are used include: arteritis of the lower limb at the intermittent claudication stage, leg ulcers of arterial origin, emboligenic arteritis with focus of platelet hyperfixation, progression of atherosclerosis as assessed by angiography, implantation of vascular surfaces, diabetic retinopathy, retinal venous thrombosis, cycle cell anaemia and perhaps thrombocythaemia. Other, more discussed indications of antiplatelet drugs are mentioned.