Other factors than prostate cancer can cause elevation of PSA levels therefore, free prostate specific antigen measurements in serum have been proposed in order to improve the specificity of laboratory identification of prostate cancer.Aim: The aim of our study was to evaluate the diagnostic significance of both total PSA and Free PSA in discriminating prostate cancer from other prostate diseases.Materials and methods: Our study group consisted of 1201 males admitted at outpatient clinic aged between 35 and 84 years old (mean age 63 years). The gene discussed is KLK3; the disease is prostate cancer.