Introduction. Prostate carcinoma (PCa) is the most common male cancer found in industrialized societies and represents a serious public health problem. Delineation of gene expression patterns in early PCa that correlate with an aggressive phenotype is a priority and may allow for radical treatment to be offered on a more selective basis to those patients with a clinically localized, yet aggressive disease. Ki-67 was recognized as associated with carcinogenesis in PCa. Aim. The aim of this study was the immunohistochemical evaluation of Ki-67 and its expression in PCa following radical prostatectomy, and analysis of its relationship to chosen clinical and morphological parameters of such tumors. Materials and methods. A total number of 56 randomly selected patients undergoing radical prostatectomy were investigated. The tumors, after fixation with 10% neutral buffered formalin, were completely embedded in paraffin. The sections were cut into hematoxylineosin staining for histological examination. The sections were also immunostained, with monoclonal antibodies against Ki-67. Immunolocalization of Ki-67 was performed using the LSAB method. Serum PSA levels were obtained from clinical information. These obtained results were statistically analyzed using the Fisher’s exact test and χ2 test. Results and Discussion. No statistically significant correlation was found between the expression of Ki-67 and the preoperative PSA level, lymph node metastases, capsular penetration, seminal vesicle invasion, and positive or negative surgical resection margins. However, a strong statistically significant correlation between Ki-67 positive and the T stage was found. We also found a relationship between the Gleason score of 7 or above and a high expression of Ki-67 in PCa (p < 0.004, p < 0.02 respectively). Conclusions. It is noteworthy that a significant correlation exists between the Gleason score and the expression of Ki-67 in this present study. We observed a high expression of Ki-67 for a Gleason score of 7 or above. Our results suggest that Ki-67 may be useful to serve as a tumor marker in PCa.