During the complex investigation of couple infertility, a group of 40 normozoospermic males having low density of semen was selected. Cytogenetic analysis revealed 2 cases of somatic karyotype aberrations: 47,XYY and 46,XY,t(14;19), and 2 cases of chromosomal polymorphisms: 46,XYq+ i 46,XY,14p+. In the article the mechanism of fertility disturbances evoked by these findings is discussed in aspects of the function of spermatozoa and its genetic material content.