SummaryIn an effort to examine the placebo, psychological deterrent, and pharmacological deterrent effects associated with implanted disulfiram, subjects were given either disulfiram implants or sham operations. Ethanol challenges elicited no disulfiram-ethanol reactions (DERs), indicating that at the time of the challenge neither a pharmacological deterrent nor a placebo effect was operating. Of the patients who resumed drinking, only those with disulfiram implants experienced DERs. Sham operation subjects continued to drink after their first post-challenge drink; four of five disulfiram implant recidivists remained abstinent following their experience of a DER. It is concluded that the pharmacological deterrent effect of the disulfiram implant may have been underestimated in previous reports.