The coupled transport of thiocyanate (SCN-) ions through binary liquid membranes of various compositions was investigated using trichloromethane and dichloromethane as membrane components in non-steady-state kinetics. The influence of the membrane composition on the kinetic parameters (k(1d), k(2m), k(2a), R-m(max),t(max)) were calculated. The present work shows the importance of the nature of binary liquid membranes in establishing transport efficiency, which is increased by varying membrane composition. Striking variations of the kinetic parameters with the membrane composition were observed. It is shown that transport kinetics obeys the competitive preferential solvation theory in the whole concentration range.