Angiogenesis is essential for tumor progression, growth and metastases. Many substances present in a normal organism can inhibit or stimulate the process of new vessel formation in tumors. The use of natural or synthetic angiogenesis inhibitors as anticancer drugs is currently under intense investigation. Such agents can have lower toxicity and are less likely to generate drug resistance than conventional cytotoxic drugs. Clinical trials are now underway to develop optimum treatment strategies for antiangiogenic drugs. This paper reviews the present achievements in preclinical and clinical studies with antitumor drugs based on inhibitors of angiogenesis.