The microhole and micropipette tip-supported interface between two immiscible electrolyte solutions (TTIES) were used to study the kinetics of ion and assisted ion transfer reactions, respectively, using the technique of ac impedance. The ion transfer reaction studied was that of tetramethylammonium transfer between water and 1,2-dichloroethane (1,2-DCE). The assisted ion transfer process investigated was that of potassium, facilitated by dibenzo-18-crown-6, between the same solvents. Tn each case, the standard apparent rate constant, k(o), was demonstrated to be a quantity which is inaccessible to measurement by electrochemical means. Both reactions were illustrated to be controlled by the diffusion of the participating species only.