Combretastatin A4 phosphate (CA4P) is the lead compound of a relatively new class of agents termed vascular disrupting agents that target existing tumor blood vessels. Rapid tumor blood flow shutdown has been demonstrated in preclinical models and patients by various techniques such as dynamic contrast-enhanced MRI, perfusion computed tomography and PET scans following CA4P infusion. CA4P typically induces rapid tumor necrosis in the center of the tumor and leaves a rim of viable cells in the periphery. In oncology, CA4P does not appear to be that active by itself, but may be more efficacious when combined with chemotherapy, antiangiogenic therapy and radiation therapy. Studies are currently underway, which combine CA4P with antiangiogenic agents. Side effects have included hypertension, tumor pain and occasional cardiovascular toxicity, without any significant myelosuppression or disabling systemic symptoms. The utility of CA4P for conditions other than cancer, which involves neovascularization such as macular degeneration, is also being explored.