There is now a substantial body of evidence that tumor growth is angiogenesis‐dependent, and that neovascularization is also necessary for tumor invasion and metastasis. In addition, the assessment of microvessel count or density in a primary tumor may ultimately prove to be a significant and independent prognostic parameter for clinical outcome with respect to tumor recurrence, metastasis, and ultimately, overall patient survival. As our knowledge of the pathways, steps, and factors involved in the underlying pathogenesis of tumor‐associate angiogenesis increases, therapeutic agents and modalities aimed at inhibiting angiogenesis by blocking one or more of these steps or factors may be devised and evaluated for their potential to inhibit cancer growth and spread. Ultimately, the inhibition of tumor‐associated angiogenesis and associated processes could conceivably form the foundation upon which the treatment of aggressive malignancies is based. Cancer 1996;78:680‐7.