In this study, we prepared polyelectrolytes to explore their effectiveness in controlling of crystallization of calcium oxalate. The effects were evaluated at different calcium to oxalate concentration ratios in the mother liquid. The polyelectrolytes affect morphology, phase, dimension and particle size distribution of the crystals. Our studies indicated that polyelectrolytes inhibit calcium oxalate monohydrate crystallization so that they are capable of increasing spontaneous nucleation of calcium oxalate dihydrate. (C) 2013 Elsevier B.V. All rights reserved.