Adsorption isotherms and adsorbed layer thicknesses were determined as a function of polymer charge density for three samples of partially hydrolyzed polyacrylamide on beta-ferric hydrous oxide particles. The amount adsorbed was found to decrease with increasing polymer charge density. Equal values of the hydrodynamic adsorbed layer thickness were measured by electric light scattering, whereas the average layer thicknesses, calculated according to R. Varoqui theory, were found to decrease with increasing polymer charge density. Information on counterion mobility was obtained by means of frequency-domain electric light scattering. The results observed are discussed in terms of counterion binding to polyelectrolytes of low charge density.