Nanoparticles of lanthanum-nickel, lanthanum-copper and barium-lead oxalates with the metal molar ratios of 1:1, 2:1 and 1:1, respectively, have been successfully synthesized in inverse microemulsions. These meta I oxalate particles of a bo ut 20 nm diameter were readily calcined into single-phase perovskite-type LaNiO3, La2CuO4 and BaPbO3. The calcination temperatures for these metal oxalates were generally 100-250 degrees C lower than those for the metal oxalates prepared by the conventional aqueous solution precipitation method. The substantial reduction in the calcination temperatures is attributed to the formation of uniform, near-spherical nanoparticles of the metal oxalate precursors obtained by the unique inverse microemulsion technique.