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The genotoxic and cytotoxiceffects of Hydroxyurea (HU) in bone marrow of male Swiss white mice Mus musculus were estimated using the Micronucleus test (mn) in PCEs (Polychromatic Erythrocytes) and DNA damage using Comet assay. Male Swiss white mice were dosed orally in single doses of 250, 500 and 1000 mg. Kg-1 b. wt, the first negative control group was given D.W and the control group carrying DMSO. The results showed significant differences in the mean values of immature erythrocytes containing micronuclei in bone marrow, in the groups treated with doses of 250, 500, and 1000 mg. Kg -1 b. wt, reached its highest value with the dose (500) mg. Kg-151.20 ±**4.15,while the mean difference with (250 ,1000)16.0 ±*4.15 and 48.80 ± **4.15,respectively, compared with the negative control 0.81 ± 2.40, and the results showed significant differences in the number of Micronuclei (mni), with the dose (500) 52.40±**4.88 compared with the control group 0.81± 2.40, mean difference micronuclei in with the doses (250, 1000) 16.0 ± 4.88 and 50.40± **4.88 , respectively, compared to the negative control.Results of comet assay showed that the treatment with hydroxyurea caused damage to the genetic material, as the mean difference cell with damaged DNA in bone marrow increased with the dose of 1000 mg. Kg-1, reaching11.40± **1.13,compared with negative control group, which amounted to 8.20 ± 0.80, while the average number of cells with damaged DNA withdosage 250 mg. Kg -1 4.40± **1.13 and with 500 mg. Kg-17.60± **1.13. The results of the present study indicate that hydroxyurea has both genotoxic and cytotoxic effects in the somatic cells of male Swiss white mice.