PURPOSE To evaluate the durability of the effect of transurethral microwave thermotherapy (TUMT) for lower urinary-tract symptoms (LUTS) suggestive of bladder outlet obstruction (BOO). PATIENTS AND METHODS A total of 841 patients with LUTS received TUMT using the Prostatron device at Sahlgrenska University Hospital, Sweden. Two treatment programs were used: low-energy Program 2.0 and high-energy Program 3.5. A questionnaire, including International Prostate Symptom Score (IPSS), quality of life (QoL) score, and questions about general health status, was sent to all the patients. The mean followup after TUMT was 8.8 years for Program 2.0 and 2.5 years for Program 3.5. RESULTS At the end of follow-up, 67% of the patients treated with Program 2.0 were satisfied with the TUMT. During the follow-up period, 37% of patients experienced worsened symptoms, 18% various complications (e.g., hematuria), and 25% transient urinary-tract infection, and 16% went into retention. Secondary treatment (repeat TUMT, transurethral resection, medical therapy) was needed in 32% of patients. The mean IPSS was 13.5, and QoL score decreased to 2.1. With Program 3.5, 82% of the patients were satisfied, with another 17% having increased symptoms, 17% various complication, 25% urinary tract infection, and 26% retention. Only 7% of patients needed secondary treatment. The IPSS and QoL score went down to 11.4 and 1.6, respectively. CONCLUSION These long-term data show that TUMT produces durable improvement and, with its safety and low retreatment rate, presents an attractive alternative for patients with LUTS suggestive of BOO.