Background: Prostatic carcinoma is a common and growing public health problem. Cyclin D1 is an amino acid that is expressed in the cell cycle and has an important role in regulating cancer progression, also, The Ki-67 protein functions as a nuclear antigen that is only expressed in proliferating cells. It is a marker of the growth fraction in malignant tissue. Objectives: to study the expression of Cyclin D1 and Ki-67 in prostatic adenocarcinoma and PIN and correlate their expression with age, preoperative serum PSA and Gleason score. Material and Methods: A total of 50 cases including 25 cases of prostatic carcinoma, 10 cases of high grade PIN and 15cases of BPH (as a control group) were studied. Tumor grade was determined according to Gleason's grading system. Cyclin D1 and Ki-67 expression was determined by IHC staining. Results: In carcinoma cases, Cyclin D1 was expressed in 23/25 cases(92%), in PIN it was expressed in 8 / 10 cases (80%) while in BPH it was expressed in only 3 /15 cases(20%). Ki-67 was expressed in 20 / 25 (80%) cancer cases, in PIN it was expressed in 7 / 10 (70%) cases while in BPH it was expressed in only 1 / 15 case (6.7%). Both Cyclin D1 and Ki-67 were significantly up-regulated in cancer cases as compared to BPH cases (P< 0.001). No significant correlation was found between the intensity of Cyclin D1 expression and Gleason score, whereas a statistically significant correlation was observed between the intensity of Ki 67 expression and Gleason score (P < 0.001). A statistically significant positive correlation was observed between Cyclin D1 and Ki-67 expression in cancer group, PIN group and BPH group with P value 0.03, 0.001 and 0.04 respectively. Conclusion: Cyclin D1 may be helpful in differentiation between BPH, PIN and adenocarcinoma of the prostate, while Ki-67 can be applied along with other prostate cancer prognostic factors.