The present invention relates generally to methods and compositions for targeting, delivering, and activating platelet-dependent vascular occlusion agents. In particular, antibodies carrying platelet binding agents are targeted to hyperplastic cells or tissues, such as the vasculature of solid tumor masses; the platelet binding agent then binds and activates platelets, which in turn bind and activate other platelets. This process results in the formation of a platelet-mediated thrombus-causing vessel occlusion.