This invention relates to novel isoxazolines and isoxazoles of formula (I): or a pharmaceutically acceptable salt or prodrug form thereof. The invention relates to novel isoxazolines which are useful as antagonists of the platelet glycoprotein IIb/IIIa fibrinogen receptor complex, to pharmaceutical compositions containing such compounds, processes for preparing such compounds, and to methods of using these compounds, alone or in combination with other therapeutic agents, for the inhibition of platelet aggregation, as thrombolytics, and/or for the treatment of thromboembolic disorders.