Nocturnal penile tumescence in the evaluation of erectile disorders: a critical review.

This article provides a critical review of the extensive literature on the nocturnal penile tumescence (NPT) method for the differential diagnosis of erectile disorders. It discusses the validity of the method and several theoretical and practical issues of importance for the adequate interpretation of results. NPT data have been considered primarily as providing a diagnostic tool for potency problems. NPT studies may contribute, in addition, significant information on central neurobiological processes that mediate male sexual function.