Background: The degree of proliferation of a tumor is closely related to the biological behavior of these tumors, there is research showing over-expression of Ki-67 in prostate adenocarcinoma that associated with increased histopathology grading which showed an aggressive tumor. Objective: The aim of this study was to determine the relations between Ki-67 immunohistochemistry (IHC) expression with histopathology grading and PSA values in prostate adenocarcinoma patients at Dr. H. Adam Malik Hospital. Methods: This study is a cross-sectional analytic study. The research was carried out in Division of Urology and Pathology Anatomy of Medicine Faculty of Sumatera Utara University at Dr. H. Adam Malik Hospital. Results: In this study, it was found that over-expression of Ki-67 as many as six patients (40%) in grade group 2 (3 + 4 = 7), while as many as 15 patients (100%) with low-expression of Ki-6. In this study, it was found over-expression of Ki-67 as many as six patients (40%) in the Gleason Score 7 to the degree of moderately differentiated histology, while as many as 15 patients (100%) on the Gleason Score â‰¤6 well-differentiated histology degrees with low-expression of Ki 67. Conclusion: There is a significant correlation between expression of Ki-67 IHC with histopathology grading adenocarcinoma of the prostate (p> 0.05). There is no significant relationship Expression of Ki-67 IHC with PSA values in prostate adenocarcinoma (p <0.05).