Does an activated oncogene that initiates tumor growth need to remain activated to maintain the cancer phenotype? This question has been answered affirmatively by experiments in which doxycycline-regulated oncogene activation induces growth of large tumors that regress completely upon oncogene inactivation--a phenomenon called oncogene addiction. We assemble here the evidence that oncogene addiction is angiogenesis-dependent. Although activated oncogenes increase tumor cell proliferation and decrease their apoptosis, these activities are not sufficient to expand tumor mass beyond a microscopic size. Oncogenes must also induce tumor angiogenesis for expansion of tumor mass. We propose experiments to validate the "endothelial centric" hypothesis of oncogene addiction.