Curcumin, one of the most studied chemopreventive agents, is a natural compound extracted from Curcuma longa L. Extensive research over the last half century has revealed that curcumin can inhibit the proliferation of various tumor cells in culture, prevent carcinogen induced cancers in rodents and inhibit the growth of human tumors in xenotransplant or orthotransplant animal models. Several phase I and phase II clinical trials indicated that curcumin is quite safe and may exhibit therapeutic efficacy. The utility of curcumin is limited by its lack of water solubility and relatively low in vivo bioavailability. Multiple approaches including nanoparticles, liposomes, micelles and phospholipid complexes are being sought to overcome these limitations. This review describes the general properties of curcumin and its potential effect against cancer including evidences of its antitumor action in vitro, in vivo, clinically and the strategies to overcome its low bioavailability.