Operant extinction contingencies can undermine the discriminative stimulus effects of drugs. Here, nicotine (0.4 mg/kg) and ethanol (0.8 g/kg) first functioned as either an S[superscript D] or S[superscript Delta], in a counterbalanced one-lever go/no-go (across sessions) operant drug discrimination procedure. Pavlovian extinction in the training context (levers removed) grossly undermined the response rates and discriminative stimulus functions of nicotine, but not ethanol; presentation of the drugs in the home cage had no impact on stimulus control for either drug but lowered overall response rates. This result was replicated between, and within, groups of rats that differed in the order of extinction phases. These data suggest that stimulus-reinforcer relationships play a role in the discriminative stimulus effects of drugs with regard to response rate, but vary pharmacologically and as a function of the context in which extinction occurs. (Contains 2 figures.)