Behavioral sensitization to amphetamine-induced stereotypy was previously shown to consist of two separable phenomena, induction and expression, both of which involve the excitatory amino acids (EAA). In the present experiments, the calcium channel blockers (CCB), nifedipine, diltiazem and verapamil, were shown to block both phenomena; these results are similar to those reported earlier for DNQX, an antagonist of the non-N-methyl-D-aspartate receptors for the EAA. The CCB, like DNQX, affect only that percentage of the stereotypic response which results from the sensitization reaction, without affecting the quantitative portion of the response attributable to the acute effect of amphetamine. The results support previous conclusions that the sensitization response consists of two quantitative components, only one of which involves the EAA. The antagonism exhibited by the CCB suggests that behavioral sensitization involves Ca++ and L-type calcium channels.