OBJECTIVE: Transurethral resection of the prostate (TURP) is still the gold standard in the treatment of benign prostatic hyperplasia (BPH). Prostate weight could be of importance on the result of transurethral microwave thermotherapy (TUMT). The present study attempted to elucidate this point. MATERIAL AND METHODS: Transurethral microwave thermotherapy (TUMT) was administered to 106 men with BPH. The patients were classified into two groups according to the weight of the prostate. Group 1 comprised 69 patients, aged 52 to 84 years (mean 65 years), whose prostate weighed up to 50 gm. Group 2 comprised 37 men, aged 55 to 87 years (mean 68 years) whose prostate weighed more than 50 gm. Prostate weight was determined by transrectal ultrasound. The protocol included history and physical examination (particularly digital rectal examination), laboratory evaluation (particularly measurement of PSA), transrectal ultrasound and uroflowmetry. The post-void residual urine was measured by urethral catheterization and ultrasound examination. RESULTS: There were 5/106 (4.7%) failure; therefore, a total of 101 patients were followed from 3 to 27 months, mean 7.7 months. Postoperatively, both groups showed improvement of all the parameters analyzed, except PSA (p < 0.01). However, comparison of the two groups for irritative and obstructive symptoms score and uroflow showed no significant difference. The decrease of the post-void residual urine was statistically greater in group 1 (p < 0.01). Group 2 showed a larger reduction in weight in comparison to group 1 (p < 0.01). Complications were observed in 12/101 (11.9%) cases, with no statistical difference between groups. Of a total of 7 patients with ejaculatory disorders, 5 patients with smaller prostate were observed. Recovery was not seen at more than 6 months follow up. CONCLUSION: The results showed no correlation between the prostatic weight and the efficiency of TUMT in the treatment of BPH.