In a triaxial creep experiment in amphibolite, we clearly found a precursory localization and development of microfractures along the final fracture plane using an AE (acoustic emission) source location technique. The precursory localization of AE hypocenters first nucleated near a pre-existing macroscopic defect and then extended gradually along the final fracture plane prior to failure. On the other hand, no significant precursory localization of AE hypocenters on the final fracture plane before failure has been reported in rock samples free of pre-existing macroscopic defects. This difference in AE occurrence patterns before failure could be explained by the difference in the degree of damage in the portion of the rock surrounding the localization zone when it nucleates. ¿ American Geophysical Union 1996