The invention concerns a method for diagnosing a prostate adenocarcinoma in a male human patient without performing a prostatic biopsy, using the PSA protein (prostate specific antigen) present in the patient's blood, serum, urine or seminal fluid that involves measuring the free PSA total level, i.e., cleaved and non-cleaved; measuring the level of all or part of the cleaved free PSA; calculating the proportion of cleaved free PSA relative to the total free PSA, non-cleaved free PSA to free PSA, and/or cleaved free PSA to any of non-cleaved free, total, or complexed PSA; and diagnosing that the patient suffers from a prostate adenocarcinoma when the ratio used is not more than a reference value or a benign pathology when the ratio used is higher than the reference value.