Objective To investigate the usefulness of percentage of free prostate specific antigen(FPSA/TPSA)/PSA density[(F/T)/PSAD]in the diagnosis of prostate cancer of PSA level in 4~10ng/ml. Methods 88 patients of PSA level in 4~10ng/ml were carried out transrectal ultrasound guided prostate biopsy. Among them,21 patients were proved to be suffering from prostate cancer,and other 67 patients were identified as benign prostate hypertrophy. The effect of F/T ratio,PSAD and(F/T)/PSAD in the diagnosis of prostate cancer were investigated. Results The mean value of(F/T)/PSAD of prostate cancer were significantly lower than benign prostate hypertrophy for patients with PSA levels in 4.0-10ng/ml, This difference has arrived statistical significance(P