Adsorption properties of two non-oxyethylene-type nonionic surfactants, sorbitan fatty acid esters (SF) and a sucrose alkanoate (SA), have been studied at the polarized nitrobenzene-water interface by measuring the double layer capacitance (C-dl). Both SF and SA lower C-dl in the range of applied potential with no sign of desorption nor of facilitation of ion transfer across the interface. The rate of transfer of tetraethylammonium ion across the interface is not appreciably affected by the presence of surfactant adsorption. Both SF and SA are effective for suppressing convective motions of the solutions in the vicinity of the liquid-liquid interface.