221 patients suffering from symptomatic benign prostatic hyperplasia (Madsen SS ≥ 8; Qmax ≤ 15 ml/s; residual urine ≤ 200 ml) were treated by transurethral microwave thermotherapy between January 1991 and April 1992 using Prostatron (Technomed Int, Rome). Very low morbidity rate and long-term complications were observed. Twelve months after treatment, the following results were observed: Madsen symptom score decreased from 11.7 ± 4.8 to 4.2 ± 4.4, peak flow rate increased from 8.9 ± 4.2 to 12.9 ± 3.7 ml/s, residual urine decreased from 134 ± 19.2 to 47 ± 41.4 ml. Pressure-flow study, performed in a subgroup, on 20 consecutive patients showed a decrease of bladder outflow obstruction in patients with prevalent constrictive obstruction, while no improvement occurred in patients with prevalent compressive obstruction. It may be deduced from these data that microwave thermotherapy is a safe technique, which may be effectively used in the treatment of BPH in patients with prevalent constrictive obstruction.