In a one year-study, 9 healthy human donors were being supplemented with beta-carotene (BC) plus canthaxanthin (CX), to determine the effect of carotenoids on chromosomal damage (micronuclei) induced in the donors' lymphocyte cell cultures by exposure to bleomycin (BLM), an antineoplastic drug that has been shown to produce chromosomal aberrations through the production of free radicals. The first four months monitoring data, including determination of carotenoid blood levels, are here reported. These data show that carotenoid supplementation significantly decrease (up to 50%) the formation of micronuclei induced by BLM in human lymphocyte cell cultures. This decrease is in correlation with carotenoid blood levels.