The present study sought to establish participation of the dopaminergic and noradrenergic mediator systems in the mechanism of induction of tolerance and physical dependence by carbamazepine and phenobarbital through influencing the phenamine-caused group toxicity and group stereotypy. In an acute experiment, treatment with a combination of phenobarbital and carbamazepine reduced the phenamine toxicity in confined animals. Phenobarbital and the combination of phenobarbital and carbamazepine prolonged the latent period of phenamine-induced stereotypy. Duration of stereotypy was lengthened by phenobarbital and carbamazepine and significantly shortened by their combination. A 14-day treatment with phenobarbital, carbamazepine and a combination of both significantly curtailed the latent period of stereotypy. After discontinuation of the treatment stereotypy duration was significantly reduced. The latent period until stereotypy occurred also shortened with varying statistical significance for the different intervals of withdrawal.