Turmeric (Curcuma longa Linn.) has been shown to inhibit chemical carcinogenesis. In this study, we compared the chemopreventive efficacy of an aqueous turmeric extract (AqTE) and its constituents, curcumin-free aqueous turmeric extract (CFAqTE) and curcumin, using the Salmonella typhimurium mutagenicity assay and the bone marrow micronucleus test in female Swiss mice. AqTE exhibited antimutagenic activity against direct-acting mutagens, 4-nitro-O-phenylenediamine and 1-methyl-3-nitro-1-nitrosoguanidine, in strains TA 98 and TA 100 respectively. Both AqTE and CFAqTE inhibited the mutagenicity of benzo [alpha]pyrene in the two strains in the presence of Aroclor-1254-induced rat liver homogenate. The inhibition in both studies was dose-dependent. Administration of AqTE, CFAqTE and curcumin at a dose of 3 mg/animal 18 h prior to i.p. benzo [alpha]pyrene injection (250 mg/kg) significantly inhibited bone marrow micronuclei formation in female Swiss mice by 43%, 76%, and 65% respectively. Furthermore, the incidence and multiplicity of forestomach tumours induced by benzo [alpha]pyrene (1 mg/animal, twice weekly, p.o. for 4 weeks) in female Swiss mice were significantly inhibited by AqTE, CFAqTE and curcumin given 2 weeks before, during and after the carcinogen treatment. These data indicate that the protection against genomic damage by turmeric extract and its components tested could be necessary for some aspects of its cancer chemoprevention.