The apparent utility of the polygraph to work both as a treatment and supervision aid and as a deterrent for future offending is cited as ample justification for its use. This article examines these claims to demonstrate that although post-conviction polygraph testing may have some utility by increasing disclosures of prior offending and, within specific cases, admissions of treatment and supervision violations, the limited evidence accumulated thus far does not adequately ascertain its accuracy nor support its efficacy or effectiveness as a deterrent. The article concludes with recommendations for creating a real evidentiary base beyond polygraph testing's apparent ability to elicit more information from offenders to evidence that can determine whether it is efficacious and effective in reducing criminality and deviance.