The invention is directed to novel PDGFRβ-specific antagonists. Theantagonists include antibodies, which can be bispecific. The antibodies areused to reduce or inhibit tumor growth and or to treat an angiogenic disease. Theinvention also includes combinations of PDGFRβ-specific antagonistswith VEGFR antagonists for such treatments. The antagonists can further be administeredin combination with other anti- angiogenic or anti-neoplastic drugs.