The role of nocturnal penile tumescence and rigidity monitoring in the evaluation of impotence.

The inability to achieve or maintain an erection of sufficient rigidity to perform sexual intercourse is a problem that affects between 10% and 20% of men at some time during their lives. Historically, the evaluation of impotence has been limited to history and psychological assessment. Nocturnal penile tumescence (NPT) monitoring is a procedure that can be used in the evaluation of impotence. Performed with appropriate measurement techniques and knowledge of the recording conditions and combined with a complete and accurate sexual history, NPT monitoring is the most effective noninvasive method of determining whether the underlying cause is organic or psychogenic.