A total of 90 patients with symptomatic benign prostatic hyperplasia (BPH) were treated with transurethral radio frequency thermotherapy. The treatment consisted of one 180-min session at 48 degrees C. All patients were evaluated before treatment and 80 (10 with urinary retention) were reevaluated at 3 months for follow-up. The analysis of the results of this group of patients is the subject of this presentation. Results were defined according to the variation in three parameters: nocturia, symptomatic score (Madsen) and urinary peak flow. Improvement (defined as a change of 50% or more in any of the three measured parameters) was found in 78% of the patients. Improvement in all of the above-mentioned parameters was found in 34.08% of the patients. In 29.82% of the patients improvement was found in two parameters and 14.02% of the patients improvement was found in one parameter and none in 21.30%. The percent variations in each parameter before and after treatment were: nocturia and symptom score decreased by 33.33% and 50%, respectively, and urinary peak flow increased by 33.65%. Age was the most important predictive factor. Of the patients under 65 years of age, 85% showed very good and good results. In comparison, only 42% of the patients over 65 years showed similar results. Immediate complications were 4 cases of acute urinary retention (5.71%) and 4 cases of urinary infection (5.71%). Transurethral radio frequency thermotherapy, having a low toxicity and complication rate, has comparable results to other nonsurgical treatment modalities. It is a viable alternative treatment for symptomatic BPH.(ABSTRACT TRUNCATED AT 250 WORDS)