Pharmacologic agents with a potential to attenuate the reinforcing properties of drugs of abuse may have an important role in the treatment of drug addiction. The reduction of drug self-administration and sweet solution intake are two common animal models employed to screen for promising therapeutic agents. When these agents are effective in suppressing the behavior maintained by drugs of abuse, the cause is usually attributed to a neuronal mechanism such as the modification of neurotransmitters that subserve reinforcement. These experiments present data for an alternate interpretation which suggest that some of these agents produce a conditioned taste aversion (CTA) that acts as a confounding variable in the screening of potential therapeutic agents. Both carbamazepine and isradipine were shown to establish a CTA at doses reported to attenuate the reinforcing properties of drugs of abuse. It is concluded that CTA represents a potential experimental confound in studies of pharmacologic agents that appear to attenuate the reinforcing properties of drugs. These results suggest that screening for a CTA is necessary in any paradigm that measures the suppression of consummatory behavior in response to pharmacologic intervention.