OBJECTIVE To analyse the outcome of patients undergoing radical prostatectomy (RP) for Gleason 8-10 clinically localized prostate cancer, and to evaluate the prognostic value of well-known predictors of progression. PATIENTS AND METHODS In all, 1480 patients had RP between 1988 and 2006, of whom 180 had pathological Gleason score >= 8 and negative lymph nodes. Biochemical progression-free survival was determined using the Kaplan-Meier method. The effect of preoperative prostate-specific antigen (PSA) level, pathological stage and margin status was assessed with univariate and multivariate analyses. RESULTS Of the 180 patients, the Gleason score in the RP specimen was 8, 9 or 10 in 70%, 27% and 3%, respectively; 24% had stage pT2 disease, 30% stage pT3a, 25% stage pT3b and 20% stage pT4a. The 5- and 7-year biochemical progression-free survival was 73 and 65% for stage pT2, 40% and 27% for stage pT3a, and 30% for stage pT3b (log rank test, P < 0.001). In the univariate model, preoperative PSA level, pathological stage and surgical margins were predictors of survival. In the multivariate analysis, preoperative PSA level and extracapsular extension predicted biochemical progression-free survival. CONCLUSIONS Gleason 8-10 tumours have a poor prognosis. Patients with a PSA level of < 10 ng/mL and stage pT2 disease have the greatest likelihood of having a longer progression-free survival after RP.