The growth and dissolution rates of NaCl crystals were investigated in a fluidized bed crystallizer. In the experiments the supersaturation and impurity concentration in the solution were varied. The growth rate was interpreted in terms of supersaturation levels. The orders and rate constants were reported. The effectiveness factors were estimated from the growth rate data to evaluate the relative magnitude of the two resistances in series, diffusion and integration. The effectiveness factor results indicate that the controlling mechanism is contributing by means of the diffusion and the integration steps on the crystal growth of NaCl from pure solution. However, the presence of impurities lead to a more important role of the integration step. (C) 2002 Elsevier Science BN. All rights reserved.