An enquiry into the lack of attention awarded to serotonin antagonism in the treatment of arterial thrombosis revealed that the mode of action of serotonin and its platelet receptor antagonists was an action upon thrombus growth, and not, as with other anti-platelet drugs upon the initiation of thrombosis. This lack of effect could explain why this approach has been considered not to be effective. However under conditions of arterial stenosis in which there is platelet activation by increased shear stress, and during the growth phase of arterial thrombi, serotonin 5HT2A antagonism has been demonstrated to have great potentcy in dispersing thrombotic obstruction to blood flow. This mode of action, the lack of participation of serotonin in haemostasis, and the absence of serotonin in wounds accounts for the proven lack of effect of effect of pure specific 5HT2A antagonists (i.e., not those with other actions) on operative bleeding and skin bleeding times. This lack of effect on haemostasis solves the dosing problem encountered with other anti-thrombotic drugs, with which drug concentration cannot be controlled with single fixed doses, leading to the association between increased anti-thrombotic efficacy and increased bleeding complications. Thus 5HT2A antagonism appears to be the preferred approach, from the point of view of safety and lack of bleeding risk; this consideration applies particularly to thrombosis therapy in the context of traumatic accidents, surgical operations and invasive procedures such as angioplasty.