Monolithic Zr65Al7.5Ni10Pd17.5 and Zr 65Al7.5Ni10Cu17.5ad plastic deformability in tension at room temperature, although Zr65Al 7.5Ni10Pd17.5 showed a large plastic strain in compression. A depressed zone that is the evidence of viscous flow deformation (so-called viscous flow depression zone; VFD-zone) was observed for Zr 65Al7.5Ni10Pd17.5 around the edge at the point of failure on its specimen surfaces. However, no VFD-zone was seen for Zr65Al7.5Ni10Cu17.5. Thus, a clear difference in tensile plastic behavior was found between Zr 65Al7.5Ni10Pd17.5 and Zr 65Al7.5Ni10Cu17.5. A structural change in the vicinity of the fracture surface of Zr65Al 7.5Ni10Pd17.5 was measured by micro-beam X-ray diffractometry (MB-XRD), We may be able to discuss the room temperature plasticity of Zr65Al7.5Ni10Cu 17.5-xPdx bulk metallic glasses correlating with the phase stability of the amorphous and icosahedral quasi-crystalline phases.