Na⁺/H⁺ exchanger regulatory factor (NHERF) and NHERF2 are PDZ motif proteins that mediate the inhibitory effect of cAMP on Na⁺/H⁺ exchanger 3 (NHE3) by facilitating the formation of a multiprotein signaling complex. With the use of antibodies specific for NHERF and NHERF2, immunocytochemical analysis of rat kidney was undertaken to determine the nephron distribution of both proteins and their colocalization with other transporters and with ezrin. NHERF was most abundant in apical membrane of proximal tubule cells, where it colocalized with ezrin and NHE3. NHERF2 was detected in the glomerulus and in other renal vascular structures. In addition, NHERF2 was strongly expressed in collecting duct principal cells, where it colocalized with ROMK. These results indicate a striking difference in the nephron distribution of NHERF and NHERF2 and suggests NHERF is most likely to be the relevant biological regulator of NHE3 in the proximal tubule, while NHERF2 may interact with ROMK or other targets in the collecting duct. The finding that NHERF isoforms occur in different cell types suggests that NHERF and NHERF2 may subserve different functions in the kidney.