It has been shown previously that ionic surface active agents (surfactants) depolarize nerve and muscle membranes and the isolated frog skin. The isolated frog skin was used in the present studies. Measurements of skin potential, short circuit current, and of Na, K, and Cl fluxes were made to determine the relative roles of inhibition of active Na transport and increases in passive ion permeability in producing the depolarization. The electrical data were in agreement with the flux data in demonstrating that lower concentrations of ionic surfactants (0.5 mM) generally inhibit the active Na transport process but have little effect on passive ion permeability. At higher concentrations (2 mM or more) surfactants produce an increase in permeability in addition to inhibiting the“Na pump”. The outside surface of the frog skin was more sensitive to the surfactants than was the inside.