Chronic prostatitis and prostatodynia are troublesome disorders that are not responsive to any kind of treatment. Patients with treatment-resistant chronic nonbacterial prostatitis (n = 61) or prostatodynia (n = 17) for longer than 3 years underwent a single 1-hour session of transurethral microwave thermotherapy (TUMT) using the Prostatron. Complete symptom disappearance was obtained in 23% of patients and a partial response in 43%. Of the patients with prostatitis, 46% showed normalization and 31% an improvement of the leukocyte count in expressed prostatic secretion. In patients with prostatodynia, the corresponding figures were 35% and 41%. Most complications were temporary, but there was one case of epididymitis and one of reduction in the volume of the ejaculate. TUMT is well tolerated and safe, and it is effective in relieving the symptoms of many patients with nonbacterial prostatitis or prostatodynia. The possible adverse effects on fertility and urinary continence require further study.