The adsorption of sodium dodecyl poly(oxyethylene) sulfate, SDE(n)S (n = 0, 3, 5, and 8), on positively charged alumina in aqueous solutions of 10 mmol dm(-3) NaCl adjusted to about pH 3.5 has been investigated by measuring adsorbed amount, zeta potential, dispersion stability, ESR, and adsolubilization for yellow OB and 2-naphthol, The adsorption of SDE(n)S increases with decreasing oxyethylene chain length of SDE(n)S, and in particular the adsorption of SDE(8)S is considerably low. The dispersion of alumina exhibits a dispersion-flocculation-redispersion process by the adsorption of SDE(n)S, which is well correlated with the change in the zeta potential of alumina. In addition, the ESR spectra of 2,2,6,6-tetramethylpiperidinyl-1-oxy(TEMPO) suggest that the microviscosity of the adsorbed layer of SDE(n)S is greater than that of the supernatant and that there are two sites for TEMPO in the SDE(3)S, SDE(5)S, and SDE(8)S adsorbed layers. Adsolubilization behaviors of yellow OB and 2-naphthol into the adsorbed layer are markedly affected by the oxyethylene chain length of SDE(n)S; the partition coefficient for yellow OB decreases with increasing oxyethylene chain length of SDE(n)S, but that for 2-naphthol shows the opposite behavior.