Because of the interest in the peat extract as a potential therapeutic agent its effect on the seminiferous epithelium cells was studied. Adult male mice were intraperitoneally injected with peat extract during 34 days. At intervals equal to the duration of the cycle of the seminiferous epithelium (every 8.5 days)., gametogenic cells were quantitatively analysed. It was revealed that the peat extract causes a decrease in the production of the A1 spermatogonia, and as a result a decrease in the intensity of spermatogenesis>. Besides, in some individuals disturbances of meiosis took place, leading to an increased degeneration of pachytene spermatocytes and formation of diploid speramtids.