A randomized, double-blind, placebo-controlled study was conducted in 43 healthy volunteers to compare the effects of policosanol (20 mg day-1), aspirin (ASA) (100 mg day-1) and combination therapy (policosanol 20 mg day-1 plus ASA 100 mg day-1) on platelet aggregation. The healthy volunteers were randomly treated for 7 days. Both, platelet aggregation and coagulation time were measured at baseline and after therapy. When policosanol was administered platelet aggregation induced by ADP (37.3%), epinephrine (32.6%) and collagen (40.5%) were significantly reduced. Meanwhile, aspirin significantly reduced platelet aggregation induced by collagen (61.4%) and epinephrine (21.9%) but not ADP-induced aggregation. Combined therapy significantly inhibited aggregation induced by all the agonists reaching the highest reductions of platelet aggregation induced by collagen (71.3%) and epinephrine (57.5%). Coagulation time did not change significantly in any group. No subject withdrew from the trial. Four volunteers reported mild adverse experiences during the study: three ASA-treated cases referred headache, epigastralgia and nose bleeding, meanwhile one patient receiving combination therapy reported gum bleeding. The present results demonstrate that policosanol (20 mg day-1) is as effective as ASA (100 mg day-1). Moreover, combination therapy shows some advantages compared with the respective monotherapies.