The zeta-potentials of anatase at pH 2-11 in 0.1, 0.3, 0.5, and 1 mol dm(-3) NaI were studied using the DT 1200 in three laboratories. At [NaI] = 1 mol dm(-3) the zeta-potentials were positive over the entire pH range. The previously observed tendency of the isoelectric point of anatase to shift to high pH at high ionic strength (M. Kosmulski, J.B. Rosenholm, J. Phys. Chem. 100 (1996) 11681) and the salt specificity of this effect were confirmed. The zeta-potentials obtained in different laboratories using DT 1200 are consistent within 3 mV. (C) 2003 Elsevier Science (USA). All rights reserved.