Anthocyanins are a ubiquitous group of water-soluble plant metabolites of the flavonoid family. They are “nature’s colors,” responsible for the blue, purple, red, and intermediate colors of leaves, flowers, vegetables, and fruits, especially berries. The daily intake of anthocyanins in the U.S. diet is estimated to be as much as 180–215 mg, or about ninefold higher than that of other flavonoids such as quercetin, genistein, and apigenin . Epidemiological studies suggest that the consumption of anthocyanins lowers the risk for diabetes, arthritis, cardiovascular disease, and cancer due, at least in part, to their anti-inflammatory and antioxidant activities . The chemistry, bioavailability, and chemopreventive effects of anthocyanins in multiple tissues have been summarized in our earlier publication  and will not be addressed here. This chapter focuses exclusively on mechanistic studies of the prevention of colorectal cancer with anthocyanins, including results from in vitro cell culture systems, in vivo animal model systems, and human studies. In addition, recent studies from our laboratory and those of our collaborators of the effects of anthocyanins on inflammation-associated colorectal cancer, that is ulcerative colitis, are discussed. Finally, this chapter summarizes the known chemopreventive effects of protocatechuic acid (PCA), a major metabolite of anthocyanins. Additional in vitro and in vivo studies of the potential preventative effects of PCA in animal model and human systems are recommended.