In　this　study,　tribological　behavior　of　a　Zr53Al16CO23.25Ag7.75　bulk　metallic　glass　(BMG)　in　air　and　phosphate　buffer　saline　(PBS)　solution　was　investigated　and　compared　with　biomedical　alloy　Ti-6Al-4V.　It　is　found　that　wear　resistance　of　the　Zr-Al-Co-Ag　BMG　sliding　in　air　is　superior　to　that　of　Ti-6Al-4V　alloy.　Under　dry　friction　condition,　wear　deterioration　of　Zr-based　BMG　is　controlled　by　oxidation　and　adhesive　wear　whereas　Ti-6Al-4V　alloy　is　jointly　dominated　by　abrasive　and　adhesive　wear.　However,　Zr-based　BMG　presents　decreased　wear　resistance　under　lubricated　friction　condition　in　comparison　with　dry　friction　condition.　In　contrast,　Ti-6Al-4V　alloy　shows　improved　wear　resistance　sliding　in　PBS.　This　is　probably　associated　with　the　inferior　pitting　corrosion　resistance　of　Zr-Al-Co-Ag　BMG　in　the　medium　containing　chloride　ions,　which　may　cause　tribocorrosion　controlled　by　synergistic　effects　of　abrasive　and　corrosive　wear.　The　possible　mechanism　for　corrosion　accelerating　wear　is　discussed　based　on　the　tribological　behavior　of　this　Zr-based　BMG.　(C)　2015　Elsevier　B.V.　All　rights　reserved.