Transurethral microwave thermotherapy (TUMT) has been shown to produce a clinical benefit in patients with symptomatic benign prostatic hyperplasia. In order to identify the features of the ideal candidate, a retrospective analysis was conducted in 32 patients who were followed for 2 mo or more. Good responders (GR) were defined as having their Siroky peak flow rate (PFR) standard deviation (SD) increase by < 0.5 or a decrease in the International Prostatic Symptom Score (I-PSS) of > 10 (22 patients). Poor responders (PR) were defined as having their PFR SD increase by < or = 0.5 and their I-PSS decrease by < or = 10 (10 patients). The prostate volume, pre-TUMT I-PSS and intravesical opening pressure were significantly greater in the GR group, while there were no significant differences between the 2 groups for the other baseline patient characteristics: age, prostate length, PFR, PFR SD, post-voiding residual volume and quality of life. Concerning the operational parameters, significantly more total energy was delivered to the prostate in the GR group (mean 131 kJ) than in the PR group (mean 101 kJ). Moreover, the 7 patients with anti-androgen therapy pre-TUMT received less total energy and 5 of the 7 were poor responders. These results suggest that patients with apparent obstructive symptoms and with moderate enlargement of prostate could benefit more from this less invasive therapy. Clinical response seems to be dose-dependent and patients with a history of recent anti-androgen treatment may have a less favorable response.(ABSTRACT TRUNCATED AT 250 WORDS)