Internal friction and micro-creep measurements were performed with high-purity Al bamboo-crystal specimens. The relaxation strength was found to decrease with the decrease of the temperature of measurement and became zero at about 0. 4T sub m, (T sub m being melting temperature). This reflects the occurrence of local disordering in the bamboo boundary region at this temperature. This result conforms to the picture of grain boundary disordering constructed by atomic simulation studies.... Grain boundary disordering, Internal friction, Microcreep, High purity al.