The objective of this study was to report on technical incidents and early and late complications occurring in high-intensity focused ultrasound (HIFU) treatment of patients with localized prostate cancer. We performed a retrospective review of patients who were treated by Ablatherm at our centre. We recorded all technical incidents, treatment discontinuations and early (o1 month) and late complications. A total of 74 HIFU procedures were performed in 65 patients (55 first-line HIFU treatments and 10 cases of salvage therapy after radiotherapy) over a 5-year period. Median followup was 41 months (10-64 months). All the procedures were well tolerated and no intra-or perioperative deaths occurred. Six technical incidents in the overall population (8.1%) led to discontinuation of the procedure. The early complication rate in patients undergoing first-line HIFU was 36.4%: urinary retention (20%), dysuria (5.4%), urinary infection (3.6%), haematuria (3.6%) and urethral stenosis (3.6%). The late complication rate was 12.7%: urethral stenosis (9%) and dysuria (3.6%). There were no cases of rectourethral fistula. The long-term urinary incontinence rate was 20% and the de novo erectile dysfunction rate was 77.1%. Nine complications (16.4%) required surgical management. The overall complication rate was 49%. Ablatherm is a reliable technique with a relatively high complication rate. However, most complications were minor and required surgical management in a few cases only. Our results confirm that all patients who are offered HIFU treatment should be properly informed of the risks, in particular with regard to continence and sexual function.