Thromboxane A2 and its immediate precursor, prostaglandin H2, induce platelet aggregation and constriction of vascular and bronchial smooth muscle. These effects are mediated through specific membrane receptors. Since these compounds have the same pharmacologic properties they are thought to share a common receptor that has been named thromboxane A2/prostaglandin H2. Evidence has accumulated in the last few years supporting the hypothesis that the platelet and vascular receptors are different. The platelet receptor has been tentatively named [TXA2/PGH2]alpha, alpha for aggregation and the vascular receptor (TXA2/PGH2]tau, tau for tone. In recent years there have been many thromboxane A2 receptor antagonists synthesized and some are now in various stages of clinical development. Based on many preclinical and some clinical studies, it appears that these drugs may prove to be of significant therapeutic benefit in a variety of cardiovascular and renal diseases.