The primary aim of our program continues to be the development of novel surface-active antithrombotic agents with emphasis on persons whose blood is exposed to biomaterials. The promising leads developed by integrating structural features from our previously reported carbocyclic derivatives and the heterocyclic congener of aspirin will be pursued further. In addition to the auspicious prospects for effective antithrombotic agents, our compounds will also serve as molecular probes for the characterization of aggregation inhibitory target sites on the platelet surface, and could well yield critically important clues for evolving biomaterial polymers void of terminal functions capable of adversely affecting platelets and, thereby, reduce the incidence of biomaterial-induced thromboembolic complications. Work on the inhibition of human blood platelet aggregation in ADP induced systems will be broadened to include evaluation of our compounds on thrombin and arachidonic acid induced aggregation. Studies on human blood platelet retention will be expanded to include biomaterial with hydrophobic characteristics, in addition to that currently employed with hydrophilic properties. Surface and interfacial tension measurements will be continued, and the interaction of our most potent compounds with mono-molecular films of entities simulating blood platelet membrane constituents will be explored.