BACKGROUND: Brachytherapy is increasingly used in the treatment of early prostate cancer, but has not been implemented as a treatment option in Norway. Recent advances in imaging techniques and the radiation technology itself has facilitated improvements in and better standardisation of brachytherapy. MATERIAL AND METHODS: An group of expert assisted the Norwegian Centre for Health Technology Assessment (SMM) in a systematic review of the evidence on the clinical effectiveness of prostate brachytherapy. The literature was identified by a defined search strategy, and assessed for relevance and validity. Only controlled or comparative studies were included in the review. RESULTS: There were no randomized controlled trials or large prospective studies. Many of the relevant studies were of poor validity. None of the included studies had sufficient follow-up for overall or disease free survival. There were no differences between brachytherapy, external beam therapy or radical prostatectomy in disease free survival (PSA measures) or in rates of complications. INTERPRETATION: There is a lack of valid data from large prospective studies on the clinical effectiveness of brachytherapy. On the other hand, the clinical effectiveness of radical prostatectomy and external beam radiotherapy is also poorly documented. Results from one large randomized controlled trial comparing radical prostatectomy with brachytherapy in the USA will not be available within the next ten years.