The tumor vessel support network offers a tantalizing target for cancer therapy, given the complete dependence of a solid neoplasia on the vasculature for both the delivery of oxygen and other nutrients, as well as the effective removal of wasteproducts. Attacking a tumor's supportive blood vessel network offers ameans of improving cancer cure rates on the basis of two principles. The first reflects evidence indicating that physiological conditions in tumors, arising primarily as a consequence of inadequate and non-uniform vascular networks, are significant contributors to resistance to non-surgical anticancer treatments. The second involves the recognition that the inherent differences between blood vessels in tumors and those associated with normal tissues provide a variety of unique targets for the design of novel therapeutics, highly selective for neoplastic growth. Therapeutic approaches that aim to destroy the tumor endothelium are being actively pursued. The application of such vascular targeting strategies as adjuvants to conventional therapeutics such as radiotherapy, offers unique opportunities to develop even more effective cancer therapies.