Male Wistar rats injected with a Cannabis sativa (marihuana) extract 3 minutes before or 30 seconds after trials, were compared to a control group for performance in a Lashley III alley maze. Animals that had received cannabis 3 minutes before trials were better performers than controls; on the other hand, posttrial injections were found to increase the running time of the subjects, although the number of errors remained the same as in the control rats. Five out of 32 rats receiving cannabis were disrupted by the treatment. These findings are discussed in the light of the perseveration-consolidation theory of memory.