We studied the binding of the muscarinic antagonist [3H]N-methyl-scopolamine [( 3H]NMS) in order to characterize muscarinic receptors located in human submandibular salivary glands obtained from intrasurgical biopsy. [3H]NMS bound with a Kd value of 1.56 nM to a single class of muscarinic receptors (Bmax 37.3 fmol/mg protein) since pirenzepine exhibited a homogeneous binding profile.