The identification of the immuno reactive molecular forms of PSA has permitted the identification of a correlation between Free PSA and Total PSA as the most important factor in the early diagnosis of prostate cancer. Cut-off of 0.15 ng/ml seems to be the most appropriate. The Authors consider that the use of this limit is important in the decision to carry out a prostate biopsy on the patients with PSA in the range of 4-10 ng/ml who have neither any clinical symptoms nor an abnormal transrectal ultrasound. In particular the sensitivity and the specificity of F/T PSA and the density of PSA (PSAD) have been compared at his limit of 0.15. In our study of 60 patients (of whom 22 were affected by cancer and 38 by BPH) we have noticed that 27/60 patients had a value of PSA between 4 and 10 ng/ml and negative DRE and TRUS. On the whole the F/T PSA report showed a slightly higher specificity than PSAD; in contrast PSAD showed a slightly higher sensitivity. In conclusion, to identify the early detection of this cancer both tests are required as well as a biopsy.