There are no reliable, sensitive, and specific clinical measures or symptoms from which to judge the severity of prostatic outflow obstruction. Urodynamics has developed the methodology for analyzing and measuring the mechanics of urinary tract voiding function in detail. There is a consensus in the urodynamic research community about realistic models of detrusor muscle mechanics and bladder outlet hydrodynamics, as is reflected in the very similar concepts proposed for clinical application. The pressure-flow diagram offers a simple graphical procedure for detailed assessment of the individual voiding balance. Most clinically relevant is the specific characterization of outlet function, because detrusor contraction strength cannot be pharmacologically influenced. It is difficult to accept that the best way to measure "prostatic obstruction" is symptom assessment rather than urodynamic measurement of the clearly mechanical entity "outlet obstruction". Urodynamics has evolved into scientifically accurate and specific techniques for voiding analysis. It is unreasonably to continue to use terms such as "outflow obstruction" or "weak detrusor" and all their synonyms in an undefined, speculative way. If we maintain that the clinical relevance of BPH is entirely related to outflow obstruction, then we must demonstrate obstruction objectively before surgery. If we aim at the treatment of symptoms alone, then we must become more specific in terminology and demonstrate that transurethral prostatic resection is indeed the optimum therapy for unobstructed symptomatic patients with BPH. Similarly, we must use the advanced urodynamic concepts to investigate the efficacy of newly suggested alternatives to resection such as prostatic balloon dilatation or pharmacologic therapy.