Iron oxide (alpha-Fe2O3) nanoparticles were deposited on the surface and in the pores of activated carbon pellets using supercritical water to synthesize the particles from a precursor solution of ferric nitrate. The dispersion of the particles in the activated carbon was found to depend mainly on the immersion time in the precursor solution at room temperature. Two types of dispersions were obtained: egg-shell dispersions at low immersion times and uniform dispersions at high immersion times. The particle size and size distribution, on the other hand, were influenced mostly by precursor concentration. Although the catalytic properties of the alpha-Fe2O3 in AC composites were not evaluated, the procedure of employing supercritical water to deposit metal oxide particles on hydrophobic surfaces inside support structures offers promise for carbon-supported catalyst preparation without the use of toxic or noxious solvents. (C) 2006 Elsevier B.V. All rights reserved.