We have observed for the first time a deposition of MgO microparticles with spherical shape. Experiment has been carried out in a small coaxial electrode system for an impulse discharge, consisting of an inner Mg-rod electrode of 1.7 mm in diameter, and an outer ring electrode, between which a small-diameter glass tube substrate is placed. From the SEM and Raman analyses, we have observed a formation of MgO particles with size less than several 500 nm. Most of the particles are spherical in shape, and distributed on the glass surface near the electrodes. The formation processes of the spherical particles are discussed. (C) 2009 Elsevier B.V. All rights reserved.