Crystal quality during zone refining is usually poor. Owing to the great density of high‐diffusivity paths, solid‐state diffusion should not be neglected. Its influence on the concentration profile is described by experiment and theory. Since the concentration gradient and curvature become very large at the end of the bar (k<1), diffusion rates are especially high in this region. A successive separation of this enriched region may lead to a considerable improvement of zone refining. Theoretical and experimental results obtained with this method will be described.