Rate of the component transfer in fluid/fluid and fluid/solid systems has been studied in an interfacial tension range of 20 to 1500 mN/m. Partial resistances to component transfer have been determined from dissolution rates of crystalline inorganic salts, from sublimation rates of organic crystals, and from vaporisation rates of pure liquids. Based on the fact that interfacial mass transfer resistances were found to be dependent on temperature, it was concluded that mass transfer through the interface was an activated process. Activation energy of mass transfer through the interface was defined as the product of the surface area required by a transferred molecule and the interfacial tension between the two phases. Based on data obtained for various systems, a relation has been formulated between the interfacial energy barrier and the interfacial mass transfer resistance.