PURPOSE: To evaluate the long-term efficacy of prostate cancer control and complication rates, in the elderly, after focal therapy with high-intensity focused ultrasound (HIFU). MATERIALS AND METHODS: Between June 1997 and March 2000, patients with localized prostate cancer were included into a focal therapy protocol. Inclusion criteria were: PSA < 10 ng/mL, < 3 positive biopsies with only 1 lobe involved, clinical stage < T2a, Gleason score < 7 (3+4), negative CT scan and bone scan. Hemi-ablation of the prostate was performed with the Ablatherm(R) device. Survival, complication rates and urinary continence were evaluated. Control biopsies were performed at 1 year. Treatment failure was defined as a positive biopsy or need for salvage therapy. RESULTS: Twelve patients with a mean age 70 years were included. Median follow-up was 10 years. Control prostate biopsies were negative in 11/12 (91%) patients. Overall survival was 83% (10/12) and cancer specific survival was 100% at 10 years. Two patients died from other causes. Recurrence free survival was 90% (95% CI; 0.71-1) at 5 years, and 38% (95% CI; 0.04-0.73) at 10 years. Five patients had salvage therapy with repeat HIFU (n = 1) or hormonal therapy (n = 4) and all salvage patients were alive at 10 years. No patients developed lymph node or bone metastasis. No patients suffered from urinary incontinence. International Prostate Symptom Score was stable at 1 year. Complications included two urinary tract infections and one episode of acute urinary retention. CONCLUSIONS: Hemi-prostate ablation with HIFU can be safely performed in selected elderly patients with adequate long-term cancer control and low complication rates. Results from larger prospective studies using improved imaging techniques and extensive biopsy protocols are awaited.