Psychostimulant-induced conditioned activity is characterized by the presence of a hyperactivity in drug-free rats exposed to an environment previously paired with the effects of a psychostimulant. This phenomenon is thought to result from a Pavlovian conditioning process. This hypothesis predicts that conditioned activity will be sensitive to perturbations known to affect classical conditioned responses. In direct contrast with this prediction, the authors report here that conditioned activity is insensitive to (a) the temporal order between the stimulant injection and the exposure to the environment, (b) unsignaled stimulant injections between drug-environment pairings, and (c) drug preexposures before the start of drug-environment pairings. It is concluded that the stimulant effects responsible for the establishment of conditioned activity may not be amenable to a Pavlovian associative process.