Many reports on anti-mutagenicity have been made with vegetables cultivated by an ordinary manner (OV). This paper presents the results of anti-mutagenicity study of organically cultivated vegetables (OCV), using water soluble chitosan for soil improvement and leaf surface spray, in comparison with that of OV. Their anti-mutagenicity were evaluated by the forward mutation assay using Salmonella typhimurium TM677. A clear difference between the juices prepared from OCV and OV was observed in the ability to inhibit the mutagenicity of authentic mutagenic compounds, 4NQO, BaP, and Trp-P-2.