In the present study we investigated the effect of zinc-deficiency on chromosomal abnormalities and mitotic index, and the interaction of zinc-deficiency and methotrexate. Therefore, two zinc-deficient and two zinc-adequate diet received mouse groups were constituted. Methotrexate was injected to one of zinc-deficient and one of zinc-adequate diet groups. There were no structural and numerical abnormalities in all groups. However, mitotic index was significantly lower than other groups in zinc-deficient and methotrexate administered mice.