Fe oxide and composite Ti-Fe oxide ultrafine particles have been prepared using sodium bis (2-ethylhexyl) sulfosuccinate (Aerosol OT; AOT)/isoctane reverse micellar solutions. Fe2O3 particles were prepared by mixing a micellar solution containing sulfuric acid solution of ammonium iron (III) sulfate with an "alkaline" or a "neutral" micellar solution containing NaOH solution or distilled water, respectively. The formation of TiO2 particles by adding titanium tetrabutoxide (TTB) to a micellar solution was also facilitated by NaOH. Simultaneous feeding of both TTB and Fe3+ solutions did not form composite particles but only Fe2O3 particles, indicating that the presence of Fe3+ prevented the formation of cores of TiO2. The TiO2 particles were thus prepared at first in the micellar solution, to which Fe3+-containing micellar solution was fed. The resulting particles possibly have a structure in which TiO2 particles are coated by Fe2O3 thin layer.