The mass transfer coefficient, k(d), surface reaction constant, k(r), and reaction rate order, r, have been calculated by applying the genetic algorithm analysis. This analysis provides the parameter estimations as new data are recorded and consequently yields the time variability of the parameters. In this study, the application of the genetic algorithm procedure is presented for determining the coefficients and their relative standard deviation. The relative standard deviation does not exceed 0.9% taking into account the crystal growth rate, R-g calculated from the equation R-g = k(r)(Delta C - R-g/k(d))(r) and the one experimentally obtained and represented by the equation R-g = k(g)(Delta C)(g), where k(r) is the rate constant for the surface reaction, ii,, is the mass transfer coefficient, I is the reaction order, ii, is the overall crystal growth rate constant, Delta C is the supersaturation and g is the overall crystal growth rate order. This new proposed method is compared with the previous methods for the cases of growth of NiSO4 and CuSO4 . 5H(2)O crystals in a fluidized bed crystallizer. (C) 2000 Elsevier Science B.V. All rights reserved.