We have studied the effect of pH on the dispersion stability of aqueous suspensions of Fe2O3 powders over a wide pH range in the presence of the poly (acrylic acid) (PAA). In order to investigate the ionization behavior of the PAA, pH of PAA solutions was measured. Sedimentation and zeta-potential measurements were conducted on aqueous Fe2O3 suspensions to characterize the dispersion stability of the suspensions. The PAA was ionized over a wide pH range and the quantity of ionization was abruptly increased at pH > 10. Thus, the dispersion of the Fe2O3 powders was observed even in acidic solutions and the dispersion stability of the suspensions increased as pH of the solutions increased. The magnitude of zeta-potential values increased with increasing pH.