The aim of the study was to investigate the effect of R-(-)-deprenyl administration on the reproductive parameters of rat males. After 30 days of intraperitoneal administration of saline or 0.0025 mg/kg (10−5 mol/l) of R-(-)-deprenyl dissolved in saline, males were mated with females of the same strain. Subsequently, animals were killed by thiopental, and their blood and sperm were collected. We found that epididymis of males exposed to R-(-)-deprenyl had higher sperm count (P<0.05), and females who mated with these males gave birth to a greater number of offspring (P<0.05) compared to control. The blood of experimental animals contained higher levels of testosterone (P<0.05), FSH (P<0.01), and total antioxidants (P<0.01). We did not detect sperm DNA fragmentation in control or in experimental males. Interestingly, round spermatids were often observed inside seminiferous tubules of experimental animals, but obviously without any negative consequences on male fertility. Our findings could be verified on a sample of human male volunteers treated for infertility, because human organism tolerate higher doses of R-(-)-deprenyl, which is a selective inhibitor of monoamine oxidase B employed in our experiment and used in the therapy of Parkinson׳s disease, rather well.