The effects of pharmacotherapeutic complete androgen deprivation treatment for 2 months before radical retropubic prostatectomy (RRP) were investigated in an open study in 375 patients. Prostate volume, tumor staging and prostate-specific antigen (PSA) were investigated as clinical parameters. The RRP specimens were analyzed particularly in terms of tumor cell regressions, pathological tumor staging and grading. Before neoadjuvant therapy (NAT) the 375 patients were classified according to stage: 36 (9.6%) were Tm; 137 (46.1%) were T2, and 166 (44.3%) were T3 stage. After NAT, the clinical investigation (digital rectal examination + transrectal ultrasonography) gave an impression of a T0 stage in 11 % of the T2 patients, and a T2 tumor stage in 39% of the T3 patients. The histopathological analysis of the initial Tib and T2 cases did not reveal any tumor in the RRP specimen in 11 (3.8%) cases, a pT2 tumor in 153 (73%) cases, and a pT3 tumor in 48 (23.5%) cases. In the patients initially classified as T3, a tumor was no longer found in 1 (0.6%) case, and a pT2 tumor was found in 48 (29.3%) cases and a pT3 tumor in 113 (67.7%) cases. Under NAT, the prostate volume fell by 34% in T3 tumors and by 24% in T2 tumors. The fall in PSA averaged 85% without significant differences in the individual tumor stages. A statistically significant correlation could not be demonstrated between the fall of PSA and the definitive pathological tumor stage. Tumor cell regressions were found in all preparations. The degree of regression was predominantly RII. These results document the direct effect on tumor cells of an inductive androgen-ablative pharmacotherapy. Regression and volume reduction of the tumor might lead to an improvement of the local surgical control. A final clinical evaluation of NAT will only be possible after long-term analysis of ongoing prospective, randomized studies.