In a recent publication,1 Johnson and Dettre attempted to criticize the equation of state approach for interfacial tensions. Their main point, in our understanding, is of a dual nature, as follows: the number of degrees of freedom for a two-component three-phase system is supposed to be one, contrary to our contention that it is two for a two-component solid-liquid-vapor system; there is, within this concept, no difference between a solid-liquidvapor system and a liquid-liquid-vapor system. Both assertions are false, as we shall show below. © 1990, American Chemical Society. All rights reserved.