The present study describes the colocalization of muscarinic acetylcholine receptors (mAChRs) and the calcium-binding protein parvalbumin (PARV) in nonpyramidal neurons of the rat dorsal hippocampus by means of dual-label immunocytochemistry. Fifty-two percent of all muscarinic cholinoceptive nonpyramidal neurons contain parvalbumin. Conversely, the vast majority (88.4%) of all PARVergic neurons possess mAChRs. The PARVergic neurons embedded within the CA1 pyramidal cell layer are nearly all (98.9%) immunopositive for mAChRs. These results indicate that the cholinergic septohippocampal projection represents a major afferent system upon the inhibitory PARVergic neurons.