The localization of muscarinic cholinergic receptor subtypes was studied in the human spinal cord using in vitro labelling of cryostat sections with [3H]quinuclidinylbenzilate (QNB) and [3H]pirenzepine (PZ) followed by autoradiography. The highest densities of [3H]QNB binding were localized in laminae II (substantia gelatinosa) and IX (motor neurons); in contrast, the highest density of [3H]PZ binding was localized to lamina II where the binding density was 22-32% higher than in lamina IX. These results suggest that the M1 and M2 muscarinic cholinergic receptor subtypes may be differentially localized in sensory and motor regions of the human spinal cord.