An immunohistochemical study on the cells proliferative activity by Ki-67 protein and localization of the matrix metalloproteinase-9 and the inhibitor of matrix metalloproteinase-1 was carried out at the benign prostatic hyperplasia (BPH) and the adenocarcinoma (AC) of different Gleason's grades. A significant decrease of the MMP-9 and TIMP-1 level in the AC of different gradations was observed. 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 a score and expression of MMP-9 (rs = -0.660) was detected. A weak negative correlation exists also between the level of proliferative activity of secretory cells and the expression of MMP-9 by tumor cells (rs = -0.369). The invasive properties of AC cells that promote a degradation of the basal membrane and connective tissue in prostate may be explained by the imbalance between the MMP-9 and TIMP-1, which expression is significantly reduced in AC, in comparison with BPH.