The effects of cannabidiol (CBD) were compared to those produced by haloperidol in rats submitted to experimental models predictive of antipsychotic activity. Several doses of CBD (15-480 mg/kg) and haloperidol (0.062-1.0 mg/kg) were tested in each model. First, CBD increased the effective doses 50% (or) ED50 of apomorphine for induction of the sniffing and biting stereotyped behaviors. In addition, both CBD and haloperidol reduced the occurrence of stereotyped biting induced by apomorphine (6.4 mg/kg), increased plasma prolactin levels and produced palpebral ptosis, as compared to control solutions. However, CBD did not induce catalepsy even at the highest doses, in contrast to haloperidol. Such a pharmacological profile is compatible with that of an "atypical" antipsychotic agent, though the mechanism of action is uncertain and may not be identical to that of the dopamine antagonists.