Disclosed are cDNAs and genomic DNAs encoding protease-activated receptor 3 (PAR3) from mouse and human, and the recombinant polypeptides expressed from such cDNAs. The recombinant receptor polypeptides, receptor fragments and analogs expressed on the surface of cells are used in methods of screening candidate compounds for their ability to act as agonists or antagonists to the effects of interaction between thrombin and PAR3. Agonists are used as therapeutics to treat wounds, thrombosis, atherosclerosis, restenosis, inflammation, and other thrombin-activated disorders. Antagonists are used as therapeutics to control blood coagulation and thereby treating heart attack and stroke. Antagonists mediate inflammatory and proliferative responses to injury as occur in normal wound healing and variety of diseases including atherosclerosis, restenosis, pulmonary inflammation (ARDS) and glomerulosclerosis. Antibodies specific for a protease-activated receptor 3 (or receptor fragment or analog) and their use as a therapeutic are also disclosed.