Single phase lead magnesium niobate, Pb(Mg1/3Nb2/3)O-3 (PMN), of high sintered density has been successfully prepared via a novel mechanochemical fabrication route. Nanocrystallites of perovskite PMN are triggered to form in a highly activated oxide composition consisting of PbO, MgO and Nb2O5. Unlike in the solid state reaction of constituent oxides at high temperatures, intermediate pyrochlore phases were not observed in the activated oxide matrix prior to the formation of perovskite PMN phase. A single phase PMN powder of perovskite structure, which consists of more or less spherical particles of 20-30 nm in size together with a minimized degree of particle agglomeration, was obtained when the constituent oxides were mechanically activated for 20 h. It was sintered to a density of similar to 99% theoretical density at 1050 degrees C for I h. Sintered PMN exhibits a peak dielectric constant of 18 083 at the Curie temperature at - 11 degrees C when measured at a frequency of 100 Hz.