In cells in culture, specific stimuli induce selective patterns of immediate-early gene induction. In the present study, we tested for such selectivity of stimulated gene expression by monitoring the expression of fos/jun gene mRNAs in the striatum in rats treated in vivo with the indirect dopamine agonist cocaine. We found by Northern blot and in situ hybridization analysis that cocaine induces the coordinate expression of c-fos and jun B mRNAs in neurons of the rat's striatum. By contrast, another immediate-early gene of the leucine- zipper family, c-jun, was not induced in striatal neurons by cocaine at any time tested from 1 to 24 hr after treatment. With the same probe, we could detect the induction of c-jun mRNA (as well as that of c-fos and jun B mRNAs) in the hippocampus following administration of pentylenetetrazol. The induction of expression of c-fos and jun B was rapid and transient, with peak expression occurring at approximately 1 hr after cocaine administration, and the induction of the two genes was in similar striatal sites. These results establish that differential patterns of expression of fos/jun genes occur in striatal neurons following exposure to cocaine, a potent psychomotor stimulant. We suggest that these tissue-specific patterns of gene expression may contribute to the response specificity of striatal neurons to stimulation by monoamines including dopamine.