Toxoplasma gondii is an intracellular parasite that causes a persistent infection in 10- 80% of the world's population, depending on geographic location. Infection with this parasite causes changes in behavior and physiological functions of an infected host, including warm- blooded animals including humans. Recent studies also show influence of infection with T.gondii on male reproductive fitness in mice and rat and to investigate this issue further became a task of my diploma thesis. In this study, detailed histometric screening of testicular function along with levels of a pituitary luteinizing hormone (LH) and screening of epigenetic modification of testicular DNA were analysed in infected and control mice. Testicular function and sperm production was significantly decreased in T. gondii positive group after a 30-day infection. The level of LH in urine of T. gondii infected mice was decreased compares to control and the number of leptotene primary spermatocytes and spermatids was lowered, but also number of Sertoli cells and tubule diameter were elevated. In epigenetic study the testicular epigenom was tested to measure global methylation and methylation of specific genes Hspa1, Crem and Creb1 which are essential for successfully ongoing spermatogenesis. The global level of methylation of...