In this paper the role and value of urodynamic measurements in symptomatic benign prostatic hyperplasia (BPH) patients selected for transurethral microwave thermotherapy (TUMT) reviewed. Although pressure-flow studies alone can diagnose benign prostatic obstruction, the level of acceptance of urodynamic investigations in BPH remains low, reportedly due to their cost and to their invasive and time-consuming nature. Furthermore, the observation that extremely different treatment modalities in BPH have nearly the same symptomatic outcome, independently of their influence on obstruction, has played a part in raising doubt as to the value of baseline urodynamics as a predictor of clinical success. Pre- and posttherapy urodynamic investigations in TUMT-treated patients have shown that urodynamic algorithms must be capable of distinguishing between compressive and constrictive types of obstruction to document the limited effects of low-energy TUMT on obstruction. Furthermore, it has been shown that urodynamics evaluated in this way seems to be the only predictor of the clinical success of TUMT when improvements in the objective parameters Qmax (peak uroflow) and residual urine are included in the definition of outcome.