The choroid plexus epithelium, CPE, secretes the major fraction of the cerebrospinal fluid, CSF. The Na⁺:HCO₃^- transporter, Ncbe/Nbcn2, in the basolateral membrane of CPE cells is important for Na⁺ dependent pH_i-increases and probably for CSF secretion. In the current study, the aniontransport inhibitor, DIDS, had no effect on the residual pH_i recovery in acidified CPE from Ncbe/Nbcn2 knockout mouse by BCECF-fluorescence microscopy in the presence of CO₂/HCO₃^- (Ncbe/Nbcn2-ko+DIDS 109% of control, p=0.76, n=5). Thus, Ncbe/Nbcn2 mediate the DIDS-sensitive Na⁺-dependent pH_i recovery in the CPE. The Na⁺/H⁺ exchanger-1, Nhe1, is proposed to mediate similar functions as Ncbe/Nbcn2 in CPE. Here, we immunolocalize the Nhe1 protein to the luminal membrane domain in mouse and human CPE. The Na⁺ dependent pH_i recovery of Nhe1 wild type mice in the absence of CO₂/HCO₃^- was abolished in the Nhe1 knockout CPE (Nhe1-ko 0.37% of Nhe1-wt, p=0.0007, n=5). In Ncbe/Nbcn2-ko mice, Nhe1 was targeted to the basolateral membrane. Nevertheless, the luminal Na⁺ dependent pH_i recovery was increased in Ncbe/Nbcn2-ko compared to wt littermates (Nhe1-ko 146% of Nhe1-wt, p=0.007, n=5). While the luminal Nhe activity was inhibited by the Nhe blocker EIPA (10µM) in the Ncbe/Nbcn2-wt, it was insensitive to the inhibitor in Ncbe/Nbcn2-ko (Ncbe/Nbcn2-ko+EIPA 100% of control, p=0.98, n=5). This indicates that a luminal, EIPA-insensitive Nhe was induced in Ncbe/Nbcn2-ko CPE and that EIPA-sensitive Nhe activity was basolateral. The Nhe1 translocation in Ncbe/Nbcn2-ko CPE may reflect a compensatory response, which provides the cells with better means of regulating pH_i or transporting Na⁺ after Ncbe/Nbcn2 disruption.