In this work, the FeNi3 permalloy nanopowder was synthesized by wire explosion in deionized water. Xray diffraction was used to identify and characterize the prepared nanopowder exhibiting a FeNi3 phase. The morphology and size of the prepared powders were observed by field emission-scanning electron microscopy and transmission electron microscopy. The compositions of the wire before exploding and the nanopowder were determined with electron probe microanalysis. The results indicate that the FeNi3 permalloy nanopowder was synthesized with an average particle size similar to 50 nm. The magnetic properties of the nanopowder indicate a symmetric hysteresis loop of ferromagnetic behavior with coercivity of 199.3 Oe and saturation magnetization of 56.7 emu/g. (C) 2009 Elsevier Ltd. All rights reserved.