Due to the unique properties of bulk metallic glasses (BMGs), BMGs have widely been used in mechanical engineering components. Although their materials design and mechanical properties have been thoroughly investigated, knowledge of their tribological behaviors is still rather lacking. Block-on-disc tests were thus conducted to investigate the friction and wear behaviors of Zr41.25Ti13.75Ni10Cu12.5Be22.5 BMGs when slid correspondingly: (i) under dry condition, (ii) in deionized water, and (iii) in solution respectively with 30%, 60% and 90% hydrogen peroxide. Results demonstrated that their friction coefficient was: (i) the lowest when slid under dry condition, and (ii) the highest when slid in 60% hydrogen peroxide solution. Moreover their best wear resistance was when slid under the dry condition and the worst when slid in the 30% hydrogen peroxide solution. Analysis of the worn surface revealed that the sliding wear mechanism of BMGs was mainly inhomogeneous plastic deformation, abrasive wear, adhesive wear, micro-cutting, oxidative wear, and peeling-off, and it changed with the change in sliding environment. (C) 2012 Published by Elsevier B.V.