Background. Despite the availability of more reliable methods for prostate biopsy, standard transrectal ultrasound-guided systematic biopsy remains widely used in the Russian Federation. However, there is a lack of multicenter studies assessing the frequency of discrepancies between pathology results obtained through radical prostatectomy (RP) and systematic biopsy. Aim. To determine the frequency of changes in the ISUP (International Society of Urological Pathology) group after RP in patients who underwent systematic biopsy for suspected prostate cancer in the Russian Federation male population. Materials and methods. Data from 603 patients who underwent RP in 6 medical institutions were collected, including 539 patients who underwent systematic biopsy. Pathological conclusions were standardized according to the ISUP grading. The frequencies of false positive and false negative results, as well as over- and underdiagnosis, were analyzed. Results. Agreement between systematic biopsy and postoperative conclusions was observed in 54.3 % of cases. The overall frequency of lowering the ISUP group was 13.1 %. False positive results were observed in 1 (0.2 %) case. Overdiagnosis of patients with clinically insignificant prostate cancer was 2.4 %, with a decrease in ISUP group from 2 and 3 to 1 in 2.2 % and 0.2 % of cases, respectively. Conversely, ISUP value upgrading was reported in 32.6 % of cases. False negative biopsy results were observed in 5 (0.9 %) cases. Underdiagnosis of patients with clinically significant forms was observed in 18.7 % of cases, with ISUP 1 initially determined after biopsy seen in 82 (15.2 %), 15 (3 %), 2 (0.4 %), and 2 (0.4 %) patients with a verified post-RP malignancy grade of ISUP 2, 3, 4, and 5, respectively. Conclusion. The high frequency of ISUP value deviations after RP compared to systematic biopsy is a serious problem necessitating the optimization of prostate cancer diagnosis and transition to more modern biopsy methods in the Russian Federation.