We used a combination of radioreceptor binding and autoradiographic techniques to study the pharmacological characteristics and anatomical localization of [3H]quinuclidinyl benzylate (QNB) in kidney sections of Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). [3H]QNB was bound by sections of rat kidney in a manner consistent with the labeling of muscarinic acetylcholine receptors. Anatomically, these receptor sites were located primarily within the smooth muscle of the renal vascular tree and to a lesser extent within cortical and medullary tubules. The density of renal muscarinic acetylcholine receptors (both vascular and tubular) was decreased in hypertension but the affinity of the ligand for muscarinic receptors was unchanged. A possible role of muscarinic acetylcholine receptors in renal function is suggested.