Rats, trained to discriminate between delta 9-THC (5 mg/kg) and a control solution, using a T-maze, were submitted to generalization tests wih delta 9-THC (2.5 and 1.25 mg/kg), CBD (40 mg/kg) and the mixtures of delta 9-THC (5 and 1.25 mg/kg) with CBD (40 mg/kg). Doses of delta 9-THC smaller than the training dose, produced a progressive reduction in the number of correct responses together with a decrease in the running time. The choice made by the animals under the effect of CBD (40 mg/kg) did not differ from that of the animals given the control solution but their running time was significantly longer. The mixtures of CBD (40 mg/kg) with delta 9-THC (5 and 1.25 mg/kg) produced approximately 50% response to both sides of the maze, and with run times greater than those observed with delta 9-THC (5 mg/kg). The results suggest that the simultaneous administration of the two cannabinoids might produce a qualitative stimulus different from that produced by delta 9-THC alone.