The tribological behavior of Ti40Zr25Ni8Cu9Be18 bulk metallic glasses (BMGs) under dry sliding and deionized water, as well as in 30%, 60%, and 90% hydrogen peroxide solution, were investigated by a block-on-disc test. This study demonstrates that the environmental conditions significantly affect the tribological behavior of the BMGs. The friction coefficient was lowest under the dry sliding condition and highest under 60% hydrogen peroxide solution. The wear resistance of BMGs was highest under the dry sliding condition, and lowest under 30% hydrogen peroxide solution. Analysis of the worn surface revealed that the Ti-based BMGs exhibited inhomogeneous plastic deformation, abrasive wear, adhesive wear, micro-cutting, and peeling off during sliding. In addition, the wear mechanism may have changed with an alteration in the environment. (C) 2011 Elsevier Ltd. All rights reserved.