The design, synthesis, and in vitro pharmacology of a new class of compounds exerting both thromboxane receptor antagonist and thromboxane synthase inhibitory activities is described. [(3-Pyridinyl)bicycloheptyl] alkanoic acid 9 and its analogues, designed with the help of molecular modeling, were synthesized and found to be inhibitors of thromboxane A2 (TxA2) biosynthesis in a human platelet microsomal preparation. The compounds were also found to antagonize both platelet and vascular TxA2 receptors. The compounds inhibited the U 46619 induced aggregation of human washed platelets and platelet-rich plasma and the U 46619 induced contraction of the dog saphenous vein.