We report on one-year results after transurethral microwave thermotherapy (TUMT) in patients with symptoms due to benign prostatic hyperplasia (BPH). The material consists of 91 cases, treated with the PRIMUS U + R device in a single, one-hour out-patient procedure. The International Prostate Symptom Score (I-PSS), S, fell from baseline 23 (17-27) to 12 (7-18.8), quality of life assessment, L, improved from 4 (3-5) to 2 (1-3) and peak urinary flow increased from 9.6 +/- 0.3 to 11.1 +/- 0.4 (ml/sec) after one year. No changes in postvoiding residuals were observed. Sixty five per cent of the patients were assessed as responders to the treatment. Complications were urinary retention and bacteriuria. Neither enlargement of prostate nor a prominent median lobe, seem to be predictors of subjective outcome. TUMT appears to be a safe and, in the majority of patients, effective measure to relieve symptoms due to BPH.