OBJECTIVE To assess the outcomes for patients with Gleason score 8-10 prostate cancer treated with brachytherapy, external beam radiotherapy (EBRT) and hormonal therapy (HT). PATIENTS AND METHODS In all, 181 patients with Gleason scores 8-10 prostate cancer were treated from 1994 to 2006 with a 103Pd implant (prescription dose 100 Gy), 45 Gy of EBRT and 9 months of HT. The median (range) follow-up was 65 (24-150) months; freedom from biochemical failure (FBF) rates were calculated using the Phoenix definition. RESULTS The 8-year actuarial FBF, freedom from distant metastases, prostate-cancer specific survival and overall survival were 73%, 80%, 87% and 79%, respectively. The pretreatment prostate-specific antigen (PSA) level significantly affected FBF, with 8-year rates of 72%, 82% and 58% for patients with PSA level of < 10, > 10-20 and > 20 ng/mL, respectively (P = 0.006). The PSA level had no significant effect on rates of distant metastases. The Gleason score had the most significant affect on FBF in a multivariate analysis, and was the only factor to significantly affect rates of distant metastases; the 8-year FBF rates were 84%, 55% and 30% for scores of 8, 9 and 10, respectively (P = 0.003). The corresponding freedom from distant metastases and prostate-cancer specific survival rates were 86%, 76%, 30% (P < 0.001) and 92%, 80%, 62.5% (P = 0.003), respectively. CONCLUSIONS The 8-year outcomes after this regimen showed favourable biochemical and distant control, as well disease-specific survival rates for patients with Gleason scores of 8-10. This treatment approach should be considered as a viable option for this subset of patients with high-risk disease.