The effects of polyacrylic acid and poly(ethylene glycol-block-acrylic acid) copolymer on the growth of calcium oxalate monohydrate (COM), a common renal stone constituent, have been investigated in aqueous solutions at 37 degrees C. A constant composition method has been utilized to investigate the crystallization kinetics of COM. The results of the experiment show that the retardation in mass transport in growth process is controlled by the nature of the polymer and its concentration. Monoclinic COM crystals were shown to be major components in the absence of polymers. In the presence of polymers monoclinic COM crystals were smaller and some of the crystals were less elongated, and small number of crystals grew in the shape of three-dimensional hexagonal prisms. The data on the growth kinetics of crystals in the presence of polyelectrolytes were examined from the standpoint of adsorption models. Polyelectrolyte effects were interpreted in terms of the adsorption of inhibitors onto the active growth sites on the crystal surface. (C) 2007 Elsevier B.V. All rights reserved.