To elucidate the precise localization of vasopressin (VP) Vj and V<sub>2</sub> receptors in the kidney, we utilized in vitro macroautoradiography (macro-ARG) and microautoradiography (micro-ARG) of these receptors in Wistar rat kidneys. This was done by using OPC-21268 and OPC-31260, two newly developed selective Vi (OPC-21268) and V<sub>2</sub> (OPC-31260) receptor antagonists. For macro-ARG, 10-μm kidney sections were incubated with Tris-HCl buffer containing [<sup>3</sup>H]-VP with or without unlabeled ligand (VP, OPC-21268, or OPC-31260) at 20°C for 40 min. These sections were then loaded into X-ray cassettes with Hyperfilm-[<sup>3</sup>H] and exposed in the dark for 2 months. The autoradiograms were quantitatively analyzed by using the research analysis system RAS 1,000; the V<sub>1</sub> and V<sub>2</sub> receptors were quantitated by subtracting the nonspecific binding (incubated with OPC-21268 and OPC-31260, respectively) from the total binding. To assess a more precise localization of the V<sub>1</sub>and V<sub>2</sub> receptors, we also investigated the micro-ARG of the renal V<sub>1</sub> and V<sub>2</sub> receptors by dipping the kidney section slides used for macro-ARG into a photographic emulsion and observing the receptors under light microscopy. [<sup>3</sup>H]-VP binding to the rat kidney was completely displaced by unlabeled excess VP, but not by unlabeled angiotensin II, indicating that [<sup>3</sup>H]-VP binding was specific for VP receptors. Computerized quantification showed that V<sub>2</sub> receptors, visualized by OPC-31260, were the predominant type of VP receptor in the kidney. Conversely, V<sub>1 </sub>receptors, visualized by OPC-21268, were fewer in number. V) receptors were partly localized to the glomerulus, cortical vessels, interstitial cells, and the medullary vessels. The V<sub>2 </sub>receptors localized to the collecting ducts and medullary tubules. Our findings indicated that renal V<sub>1</sub> and V<sub>2</sub> receptors can be detected by in vitro macro- and micro-ARG by using OPC-21268 and OPC-31260.