The inhibitory activity of saffron extract was studied on human platelets. Platelet aggregation and lipid peroxidation were evaluated with platelet rich plasma (PRP) and platelet membranes respectively obtained from blood of healthy human volunteers. Human platelets were subjected to stimulation with a variety of agonists like ADP (61 microM), epinephrine (76 microM), collagen (11 microg/ml), calcium ionophore A 23187 (6 microM) and ristocetin (1.25 microg/ml) in the presence and absence of saffron extract with IC50 being 0.66, 0.35, 0.86 and 0.59 mg respectively and no inhibition with ristocetin. The inhibitory effect was dose dependent with concentrations varying between 0.16 to 0.80 mg and time dependent at IC50. A significant decrease was observed in malondialdehyde (MDA) formed, one of the end products of arachidonic acid metabolism and of serotonin released from dense granules of platelets at respective IC50. Lipid peroxidation in platelet membranes induced by iron-ascorbic acid system was inhibited by saffron extract significantly with IC50 of 0.33 mg. Hence, it may be said that aqueous extract of saffron may have component(s), which protect platelets from aggregation and lipid peroxidation.