Section headings and selected papers: Foreword. Theoretical Developments. Impurity diffusion in a doubly-doped elemental semiconductor with pair formation, D J Young et al. Kirkendall and vacancy correlation effects in ternary diffusion, J S Kirkaldy. Initial-value solutions for spinodal decomposition in ternary solids, J S Kirkaldy et al. The continuum theory of nucleation in multicomponent systems, J J Hoyt. Experimental Developments. Diffusion in a two-phase region of the Fe-Cr-Al system, J Stringer & H C Akuezue. Selected multiphase diffusion structures in the Cu-Ni-Zn system, M A Dayananda & C-L Liu. Periodic structures in multicomponent diffusion couples, F J J Van Loo & K Osinski. A methodology for obtaining diffusion coefficients in a three-phase ternary couple: GaAs/nickel, C H Jan et al. Applications. Multicomponent diffusion interactions in gels: zeolites, polymers and slags, D Okongwu & J S Kirkaldy. Computer simulation of multicomponent diffusional transformatons in steel, J O Anderson et al. Decomposition of multicomponent austenite in spheroidal graphite cast irons, D Venugopalan. A first-order solute-drag theory for the effects of alloying elements on the growth of proeutectoid ferrite in steels, G R Purdy & Y J M Brechet. Authors' index. Subject index.