Carnosol is an ortho-diphenolic diterpene with an abietane carbon skeleton with hydroxyl groups at positions C-11 and C-12 and a lactone moiety across the B ring. Carnosol is the product of oxidative degradation of carnosic acid. Carnosol is a naturally occurring phytopolyphenol found in rosemary that functions as an antioxidant, antimicrobial, and anticarcinogen. Carnosol has been shown to inhibit inductions of COX-2 by blocking PKC signaling. Carnosol is an inhibitor of AR and ER α. Several pre-clinical studies have suggested that carnosol selectively targets tumorigenic cell as opposed to non-tumorigenic cells and is safe and tolerable in animals. Carnosol has been shown to elicit chemopreventive effects by (1) blocking the bioactivation of carcinogens, (2) enhancing antioxidant and/or detoxification enzyme activities, (3) suppressing tumor-promoting inflammation, (4) inhibiting cell proliferation and inducing apoptosis selectively in cancer cells, and (5) blocking tumor angiogenesis and invasion.