Potential-step chronofluorometry, a new approach based on the measurement of the change in fluorescence intensity accompanied by interfacial ion transfer, has been applied to the study of the kinetics of Eosin Y dianions (EY2-) transfer across the 1,2-dichloroethane (DCE)/water (W) interface. The standard rate constant is found to be 9.5 x 10(-3) cm s(-1) at 24 degrees C. This is an order of magnitude smaller than the value predicted by the Stokes’ law and its diffusion coefficient in water, indicating the presence of greater friction against ion transfer at the interface. The dependence of the logarithm of the rate constant on the applied potential has a convex curvature, which does not conform to the Butler-Volmer current-potential characteristic with a potential-independent transfer coefficient. The observed curvature and the fact that the apparent transfer coefficient at the formal potential is 0.5 are instead well explained by the Goldman-type current-potential characteristic, which is based on the Nernst-Planck equation with the Goldman-type approximation, i.e., linear variation of electrochemical potential across the interfacial layer. The rate-determining step of the EY2- ion transfer across the DCE/W interface can therefore be understood phenomenologically as an activationless process, as is the ion transport in homogeneous solution phase. The inadequacy of the Frumkin-type double-layer correction to the kinetics of charge transfer is suggested.