The forward transfer kinetics of a water-soluble cationic dye (dimidium) across the planar interface from a conjugate aqueous phase to a water-in-oil (w/o) microemulsion phase (formed using the anionic surfactant Aerosol-OT) have been investigated by means of a rotating diffusion cell. By measurement of the solute flux as a function of rotation speed of the diffusion cell membrane, the influence of mass transport effects to and from the interface could be controlled and eliminated by extrapolation to infinite rotation speed. The rate of forward transfer was linearly proportional to the concentration of solute in the aqueous phase; i.e., it was not possible to saturate the aqueous side of the interface. The rate, however, was found to reach a limiting value on increasing the concentration of nano water droplets in the microemulsion phase. This is explained by a transport model in which the dye initially partitions to the aqueous side of the interface; it then enters the organic phase inside a forming water droplet. The rate of back transfer of H+ from a microemulsion droplet phase into a coexisting water phase has also been studied as a function of droplet concentration and temperature. These results extend previous measurements on the same system. It is shown that enthalpy-entropy compensation effects operate for the rate-determining step. In our proposed model for defining dynamics of interface transfer from or to an aqueous phase in Winsor-II systems, the rate-determining step is the same for forward and back transfer and is concerned with droplet coalescence with the interface.