Abstract When rhizome juice of ginger, Zingiber officinale, was added to a solution of 2(2-furyl)-3-(5-nitro-2-furyl)acryl amide (AF2) or N-methyl- N′-nitro- N-nitro-soguanidine (NTG), mutagenesis by these chemicals was markedly increased. As a result of the component fractionation of the ginger juice, it was found that -gingerol was a potent mutagen. However, the ginger juice also contained anti-mutagenic component(s) against -gingerol (CAS No. 58253-27-3) (present study) and tryptophan pyrolysates (Kada et al., 1978; Morita et al., 1978). It is suggested, therefore, that the -gingerol component may be mutagenically activated by the presence of AF2 and NTG.