Canthaxanthin is a carotenoid terpene pigment initially found in various sources including plants and fish. Canthaxanthin exhibits immunostimulatory, antioxidative, and chemopreventive activities; it does not display any vitamin A activity. In vivo, canthaxanthin increases cell-mediated and humoral immune responses. Metabolites of canthaxanthin enhance gap junction communication and expression of connexin 43. In vitro, canthaxanthin inhibits t-BOOH-induced production of malondialdehyde and lipid peroxidation; it also scavenges radicals. In other cellular models, this compound inhibits MCA-induced neoplastic transformation, suppressing carcinogenesis.