Prostate cancer is the second frequent cause of cancer among men. Prostate Specific Antigen ( PSA) is used widely for the diagnosis and during the follow-up of the patients as well as to distinguish prostatic hyperplasia from prostate cancer. However, PSA values above the reference range may be found also in nonmalignant conditions. Conversely, not all prostate cancers give rise to an elevated serum PSA concentration, Therefore, new and reliable parameters have been investigated. The ratio of free / total PSA has been found to distinguish between prostatic hyperplasia and carcinoma. It has been suggested that creatine kinase (CK) and acid phosphatase (ACP) isoenzymes may show significant variation in prostate cancer. In this study, free and total PSA levels and CK and ACP isoenzyme levels were investigated in patients with prostate cancer and prostatic hyperplasia, A significant difference between the ACP levels was found. Total PSA values were higher in cancer patients. The diagnostic sensitivity and specificity for prostatic cancer was clearly increased by considering the free / total PSA ratio. A higher specificitiy was achieved by the combination of the three parameters.