We assessed the antithrombotic activity of some simple organosulfur compounds which have some of the functionality found in the disulfide ajoene, a pharmacologically active compound isolated from garlic. The results establish that antithrombotic activity is associated with disulfides directly attached to a phenyl ring and is further enhanced by an alpha-sulfonyl group. CH3SO2CH2SSPh proved to be a potent inhibitor of platelet aggregation with an IC50 of 5 mu M.