The influence of the food dyes E160e (beta-apo-8'-carotenal in an oil suspension) and E160a (beta-carotene in an oil suspension) on clastogenic effects of cyclophosphamide (CP) and dioxidine (DN) was investigated. Chromosome damage in the bone marrow of C57BL/6 mice was reported. The following protocols were used: (1) simultaneous single administration of the dye and the mutagen and the subsequent animal sacrifice within 24 hr; (2) a 4-day pretreatment with the dye (daily administrations) followed with simultaneous injection of the dye and the mutagen on the 5th day 24 hr before sacrifice; (3) daily co-administration of the dye and the mutagen for 5 days with sacrifice 6 hr after the last administration. CP at a dose of 30 mg/kg and DN at 300 mg/kg were injected intraperitoneally; the dyes at doses of 0.5, 5 and 50 mg/kg were given orally. Under all the protocols applied, E160e at a dose of 50 mg/kg caused a significant reduction of both DN and CP effects. At 5 mg/kg this dye reduced the effects of the mutagens only under the pretreatment regimen. Pretreatment with E160a at doses of 5 and 50 mg/kg resulted in a meaningful reduction of the DN effect. Under the combined treatment with mutagens this dye reduced both CP and DN effects.