The epithelial Na⁺ channel (ENaC) mediates the Na⁺ uptake in tight epithelia from the luminal side into the cells by using a gradient that is maintained by the basolateral Na⁺/K⁺-ATPase. For our experiments we expressed rat-ENaC in Xenopus laevis oocytes. Conventional two-microelectrode voltage clamp in combination with special hard- and software enabled us to monitor ENaC current (I_m), conductance (G_m) and capacitance (C_m) simultaneously. Previously, we reported that the ENaC expression is strongly dependent on the intracellular Na⁺ concentration [Na⁺]_i and follows a bell-shaped curve with maximum ENaC current and conductance at 10 mM intracellular Na⁺. To extend and confirm these data we used EGFP-ENaC and determined the fluorescence intensity by means of fluorescence microscopy. We found a peak in fluorescence intensity at 10 mM [Na⁺]_i. In another set of experiment we substituted Li⁺ for Na⁺. Li⁺ is well conducted by ENaC and showed the same positive effects as [Na⁺]_i on ENaC expression. Yet, with Li⁺ as the Na⁺ replacing anion we found that the maximal effect of Li⁺ already occurred at a Li⁺ concentration of 5 mM. We conclude that, at least in Xenopus oocytes, expression of ENaC is dependent on [Na⁺]_i or [Li⁺]_i.