Policosanol is the trivial name of a mixture of high molecular weight alcohols isolated from sugar cane, wherein octacosanol is the main component. The effects of Policosanol treatment on rat platelet aggregation were studied. Depending on the dose, Policosanol (5-20 mg/kg, perorally) inhibited the decrease in circulating platelet counts and collagen-induced malondialdehyde concentration in plasma. In rat clotted whole blood thromboxane B2 formation was inhibited by Policosanol (25 mg/kg). Policosanol (50-200 mg/kg, single doses) inhibited ADP-induced platelet aggregation in platelet-rich plasma, while lower doses (25 mg/kg) did not change responses to ADP significantly. However, rats treated with this dose (25 mg/kg) for 4 weeks showed a significant inhibition of platelet aggregation in PRP when a submaximal ADP concentrations was administered.