Under the influence of natural gas containing hydrogen sulfate, it has been found that the level of malondialdehyde was increased in testicular tissue in experimental animals as well as in ejaculate in men employed in gas and oil industry. It has been established that a considerable decrease in the gen-eral quantity of spermatogenic cells took place by more than 7 times compared with the control group; the number of epididymal spermatozoa in rats was decreased by 70 %, necrosis of spermatogenic epi-thelium took place. Considerable decrease in the diameters of seminal tubules on the background of interstitial tissue proliferation at the expense of small Leydig’s cells was found to take place. Experi-mental and clinical data show the same tendencies by indexes of lipoperoxidation at the level of testis under the influence of analogical stressing factors. Spermatozoid concentration in men was found to be decreased by as many as 10times more than in the control group. The leading defects of spermato-zoa were the neck and tail pathologies.