AbstractA general treatment of entry region multicomponent mass transfer between a fully developed turbulent flow and a smooth pipe wall has been developed from a basis first derived by Toor.The couled multicomponent equations were reduced to an equivalent binary system by the method of undetermined constants. Numerical solutions for a forced convection, binary diffusion system involving gas‐phase, nonequimolal diffusion were applied to a ternary system. These solutions have been found to compare well with these authors entry region mass transfer data on a ternary acetone‐methonal‐air mixture and with the earlier analogy theories derived for the case of an infinitely long test section.We conclude that there is a significant interaction in some multicomponent systems, enough that the binary theory can not be satisfactorily applied in the design of multicomponent mass transfer sy