Antimutagenicity of the water extracts prepared from the outer or inner portion of storage roots (hereafter referred to as ‘outer and/or inner portion’) of 4 varieties of sweetpotato differing in the flesh color was investigated using Salmonella typhimurium TA 98 to determine the distribution of the antimutagenic components. Analysis of anthocyanin pigments in both portions revealed a large distribution of anthocyanin pigments in the outer portion and showed that the content of cyanidin in the outer portion was higher than in the inner one. The strong antimutagenicity of Ayamurasaki outer portion was attributed chiefly to the high concentration of cyanidin. The extracts from the outer portions of Koganesengan, Sunny Red, and Joy White varieties showed an antimutagenic activity unlike the inner ones, suggesting that the antimutagenic component in the outer portions of these varieties was mainly associated with phenolics.