Transurethral microwave thermotherapy (TUMT)has emerged as an attractive alternative to standard prostatectomy for benign prostatic hyperplasia (BPH). The World Health Organiza- tion consultation for BPH recommended high-energy TUMT (ie, the Targis system, 2000)for the treatment of symptomatic BPH. TUMT can be administered in a single 30-minute to 1-hour outpatient treatment session under local anesthesia. BPH patients experience significant im- provement in condition and quality of life, and treatment-associated morbidity is low. The aim of heat therapy is to destroy BPH tissue without damaging the structures surrounding the treated organ, namely the sphincter, bladder wall, rectum, and urethra. Tissue destruction results from coagulative necrosis caused by heating the target area over 44C. These two fea- tures characterize TUMT and distinguish it from hyperthermia using microwaves or transure- thral radiofrequency. Transurethral microwave treatment systems Significant differences exist between microwave treatment systems. These differences pertain to microwave antenna design, generated heating patterns, and treatment protocol and must be taken into account when evaluating results of various TUMT studies. TUMT was pioneered using the Prostatron microwave system (Technomed Medical Systems, Lyons, France), and this system has been by far the most extensively investigated. Recently, a high-energy modification of the Prostatron treatment protocol, designed to provide enhanced treatment efficacy, was introduced. This protocol is based on a modification of the original Prostasoft version 2.0 software to allow a maximum of 80 W microwave power to be applied during TUMT with use of the new Prostasoft version 3.5. To date few studies have directly compared treatment responses between the high- and low-energy Prostatron protocols corresponding, respectively, to the version 2.5 and 2.0 software (Figs. 1-3). The more recently developed Targis microwave system (Urologix, Minneapolis, MN)has also been the subject of numerous investigations. Additional microwave treatment systems inves- tigated in clinical trials to date include the Microthermer (Laser Electro Optics, London, UK), ECP (Comair, Stockholm, Sweden), Prostalund (Lund Instruments AB, Lund, Sweden), Urowave (Dornier Medizintechnik GmbH, Germering, Germany), Prostcare (Bruker Medical, Wissembourg, France), and Thermex-II (Direx, Petah Tiqva, Israel).