Iimmunohistochemical study of cells proliferative activity by Ki-67 protein and localization of matrix metalloproteinase-9 (MMP-9) has been carried out at benign prostatic hyperplasia and adenocarcinoma of different gradations by the Gleason score. A significant decrease of the MMP-9 levels in the adenocarcinoma of different gradations have been found. A moderate positive correlation between the Gleason score and cell proliferation Ki-67 index (rs = 0.674) and a moderate negative correlation with the level of such score and expression of MMP-9 (rs = –0.660) were detected