The effects of acidic additives on the size and shape of the monodispersed ferric(hydrous) oxide par-ticles prepared by forced hydrolysis from aqueous ferric chloride solutions, were investigated by transmission and scanning electron microscopes. Incubation 0.02M ferric chloride solutions for 48 hours at 100℃ with sodium and potassium phosphates, citric acid and tartaric acid, various shapes of particles were produced with the retardation of the growth rates of hematite as the concentrations increased. On the other hand, the addition of oxalic acid, acetic acid and sodium hydrogen carbonate formed more spherical shapes without affecting the growth rate of hematite. The shape and growth of particles with additives is attributed to the adsorption of additives on the preferred surface that con-trols the morphology of particles and the phase transformation from β-FeOOH to α-Fe₂O₃.