The aim of this study was to evaluate the effect of hyperbaric oxygen treatment (HBO) to the vigilance of spermatozoids. The sperm samples were obtained from the patients (n=10) with diagnosed oligospermia. The motility of spermatozoids in tested samples was not lower than 30% but it did not exceed the critical proportion of 50%. Three groups of samples were formed, with respectively 10 samples in each group. All of them were exposed to HBO conditions of 2.5 ATA for 90 minutes. Group I was exposed to HBO conditions without any addition of medium. Group II was added 5 ml of EBSS solution. Tyrode’s solution in volume of 5 ml was added to group III. The evaluation of functional characteristics of sperm was carried out 30 minutes after completion of HBO treatment. Statistically significant increased in motor activity was registered in three all groups (p<0.05). The biggest increased in vigilance of spermatozoids was found in the samples of the group III (p<0.01), exceeding the critical proportion of 50% in all of the samples. The obtained results suggest that the acute exposure of the sperm samples to HBO has favorable impact to functional capacity of spermatozoids in view of their better motility. Mitrović, Brkić, Jovanović, , , , , , (2011). The effects of hyperbaric oxygen treatment on vigility of spermatozoids: preliminary report. Acta physiologica Hungarica, 2011 Mar;98(1):85-90. https://www.ncbi.nlm.nih.gov/pubmed/21388934