The devitrification behavior and phase formation in Zr65-55Ni10Al7.5Cu7.5Ti5-10(Nb,Ta)(5-10) metallic glass have been studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. It has been found that mutual addition of Ti and Ta/Nb benefits the formation of nanoscale icosahedral phase in the glassy phase on heating and the oxygen content in the alloy makes significant influence on the devitrification behavior of these alloys. At the same time in Nb-bearing alloys and alloys containing 5 at.% Ta icosahedral phase was found to coexist with crystalline one. (C) 2004 Published by Elsevier Ltd.