The penile plethysmograph is a device which measures male sexual arousal by means of a transducer around the subjects’ penis while various stimuli are
presented. Although this seems to be a simple enough premise, half a century of research has failed to demonstrate that the assessment is either reliable or valid.
It does, however, seem to be a significant predictor of risk. This chapter reviews the literature around the reliability and validity of phallometric assessment, the limitations to its use, its contribution to risk
assessment, and alternatives to its use, and concludes with remarks on the future of the phallometry
