Δ8-Tetrahydrocannabinoquinone (HU-336) is a potent antiangiogenic agent. Δ8-Tetrahydrocannabinoquinone inhibits angiogenesis by directly inducing apoptosis of vascular endothelial cells without changing the expression of pro- and antiangiogenic cytokines andreceptors. Δ8-Tetrahydrocannabinoquinone is highly effective against tumor xenografts in nude mice.