Diffusion processes in quasiternary systems are described by a diffusion matrix composed of a matrix covering the kinetic properties and a matrix describing thermodynamic influences by interaction parameters. The interdiffusion processes were simulated by a computer program and the calculated reaction paths were compared with earlier reported experimental data. It can be shown that thermodynamics governs the principal reaction paths, whereas the individual diffusion behavior is controlled by the kinetic matrix composed of tracer diffusion coefficients. Regions of uphill diffusion do occur not only in real, but even in ideal systems. (c) 2006 Elsevier B.V. All rights reserved.