The influence of the concentration boundary layers on membrane potential in a single-membrane system on basis of the Kedem-Katchalsky equations was described in cases of horizontally mounted neutral membrane separates mechanically stirred and unstirred binary electrolytic solutions at different concentrations. The measure of this influence is following expression Delta psi(CBL) = Delta psi(m)-Delta psi(s), in which Delta psi(m) is a membrane potential in conditions of well-stirred solutions and Delta psi(m) - potential in conditions of unstirred solutions. Results of five sets of calculations were presented. In first the Delta psi(CBL) as a function of ratio solution concentrations (C-h/C-t) at constant value of concentration Rayleigh number (R-C) was calculated, in second - the Delta psi(CBL) as a function of R-C at constant of C-h/C-t, in third - the Delta psi(CBL) as a function of R-C at constant concentration polarization coefficient (zeta s), in fourth - the critical values of Rayleigh number (RC)(crit) as a function of zeta s at constant of C-h/C-t and in fifth - the Delta psi(CBL))(max) as a function of (, at constant of C-h/C-t. Calculations were made for the case where on a one side of the membrane aqueous solution of NaCl at steady concentration 10(-3) Mol 1(-1) (C-t) was placed and on the other aqueous solutions of NaCl at concentrations from 10-3 Mol 1(-1)10(-2) Mol 1(-1) (Cl). Their densities were greater than NaCl solution's at 10-3 mol 1-1. It was shown that voltage concentration boundary layers effect depends on hydrodynamic state of a complex concentration boundary layer-membrane-concentration boundary layer, what is controlled by R-C and zeta s.