To date transurethral laser ablation of the prostate (TULAP) in benign prostatic hyperplasia (BPH) is the commonest form of transurethral laser surgery. The invention of the so-called "sidefire" laser fibre was the prerequisite condition for effective transurethral laser ablation of the prostate. Since the first transurethral laser ablation in human BPH was performed by Costello in September 1990, a multitude of urologists have adopted this technique. In the meantime, a great many studies have been carried out and a lot of data have been published. The initial, to some extent euphoric, enthusiasm of some urologists as well as some patients, especially in the USA and Europe, has turned into a more critical reflection. There is no doubt at all that TULAP is a feasible alternative treatment method with reasonable results. Especially in the high-risk patient, there is neither severe blood loss nor an uptake of irrigation fluid. It is also beneficial to allow unlimited treatment in patients on anticoagulant medication. Nevertheless, the value of TULAP in comparison to transurethral electroresection of the prostate (TURP), generally accepted as the "gold-standard" in the surgical therapy of BPH, remains unclear. A final assessment will only be possible when further data on mortality, short and long term morbidity and outcome with this method have been presented. Strong evidence exists that the operation can be performed without blood loss and uptake of irrigation fluid. A further advantage seems to be preservation of sexual function, especially anterograde ejaculation in the majority of patients, in comparison to the "gold-standard" TURP. In most studies, the value of TULAP is further compared with regard to the elimination of obstruction by means of pressure-flow-studies. The aspect most frequently neglected by all investigators to date is the frequency and severity of urinary tract infections (UTI) in patients in whom TULAP is performed. Basically, UTI in the form of cystitis, ascending infections such as male adnexitis or pyelonephritis, prostatitis of the remaining parts of the prostate and catheter-induced urethritis are associated with transurethral surgery in general. Certain data indicate an age-related frequency of UTI. From a rate of approximately 1% of UTI in infants, the frequency rises to 30% in the 8th decade of life. According to these data, one can expect that in a study of TULAP in high risk patients, most of whom are elderly, a large number present for surgery with a preexisting UTI. Other data demonstrate that after 4.5 days 50% and more of patients with an indwelling catheter develop an ascending UTI, although a closed urinary drainage system has been used. In most cases enterobacteriaceae, in 80% Escherichia coli, are detected. Especially in TULAP, a period of prolonged catheterisation has to be expected in the majority of patients. The risk of UTI in the perioperative phase is therefore expected to be higher. There are several higher risks and possibilities of complications in transurethral surgery in patients with UTI. Taking this into account, all our patients routinely undergo low dose antibiotic prophylactic treatment. The frequency of infections of the remaining parts of the prostate after prostatic surgery is strongly correlated to the flow characteristics in the prostatic urethra and to the amount of destruction of the prostatic tissue. Here are further reasons for a higher risk of infection after TULAP. Due to the fact that the prostatic tissue is not removed by a clear cut, but coagulated by laser beam, a rough surface due to tissue necrosis results. This is an ideal culture medium for bacteria aggravated by the disturbed laminar flow in the prostatic urethra, which favours an intraprostatic reflux of infected urine. There is evidence that UTI are the most important factor of morbidity during the first weeks after TULAP because of their bothersome symptoms.(ABSTRACT TRUNCATED)