In this study, the nanoindentation behavior of a Cu-Zr-Al-Ag bulk metallic glass was investigated at various loading rates. It is found that the load-displacement curve of indentation exhibits a significant serration of displacement jumps (pop-ins). The experiment data show that the depths of the pop-in site are a geometric series. The size of pop-ins increases with indentation depth but decreases with loading rate; a larger applied loading rate leads to smaller pop-ins during the indentation process. However, the experimental results indicate that the loading rate has no influence on the depth ratio of pop-in sites. FIB observation and TEM diffraction patterns show that the microstructure of the BMG material remained amorphous irrespective of the presence shear bands. (C) 2010 Elsevier B.V. All rights reserved.