Some of the causes of male infertility may have their origin in epigenetic disorders during prenatal life. The aim of the study was to investigate DNA methylation of LINE-1 transposon repetitive sequences and the imprinted differentially methylated region (DMR) of H19 gene in human and rat fetal testis and the RB1 tumor supressor gene in humans in parallel with the expression of RB1 protein and its phosphorylated forms. DNA methylation in the fetal rat testis increases significantly for LINE-1 from 16.5 to 21.5 dpc, and for H19 to 17.5 dpc. Analysis of human samples showed a high level of LINE-1 methylation during pregnancy with a significant decrease in puberty, and for H19 an increase until the end of pregnancy, while RB1 was hypomethylated during pregnancy (below 5%). The expression of Ki-67 proliferation marker in the rat testis is significantly reduced from 16.5 to 19.5 dpc as well as the expression of phosphorylated RB1 proteins from 16.5 and 19.5 relative to total cell number and tubular diameter, and is increased from 19.5 to 20.5. In human testes, the expression of Ki-67 and phosphorylated RB1 in relation to the total number of cells and the diameter of the tubules decreases from the first to the second trimester, and from the second to the third the total RB1 and a part of the phosphorylated forms increase. The results of this work are important as a basis for further research into the causes of infertility or testicular tumors that may be caused by altered methylation of genes that affect genome stability, genomic imprinting, and cell cycle regulation.