[en] The radiogenotoxicological effect such as chromosome aberrations in germ cells and abnormalities in sperm induced by fission fragment ¹⁴⁷Pm in different periods after iv this radionuclide to mice was observed. Results indicated that chromosome aberrations of spermatogonium were induced by ¹⁴⁷Pm. The chromosome aberration rates and polyploid cells number were increased with the periods of contamination of ¹⁴⁷Pm. At the same time ¹⁴⁷Pm also induced chromosome fragments and translocations of primary spermatocyte. It was shown that polyvalent of primary spermatocyte appeared only after 10 days of ¹⁴⁷Pm contamination