A study has been made of the dependence of a membrane potential produced by adsorbed ANS anions on their bulk concentration, on the ionic strength of the solution, on the magnitude of charge and dipole potential drop at the bilayer surface. Measurements have been made on artificial planar membranes of various composition by the inner field compensation method. On membranes of neutral lipids the ionic strength dependence was absent, while on charged BLM an increase in ionic strength resulted in a parallel shift of the potential dependence on ANS bulk concentration. A theory previously developed has been used for the interpretation of our results. It is assumed there that the adsorption plane of ANS ions is located within the membrane and account is taken of the discrete charge effect and the non-electric interaction of ions in the adsorption plane.