Zone refining was applied experimentally to high-purity aluminium produced by a combination of the three-layer electrolytic refining process and the segregation process. The cropping procedure was effective in increasing tlie efficiency of zone refining. 'The highest residual resistance ratio R(300K)iR(4.2K) obtained was more than I50 000 in the bulk value, corresponding to a refined purity better than 99.99999 %.