Differential and integral parameter estimation techniques were used in this work to estimate aluminum trihydroxide crystallization kinetics (i.e., growth, agglomeration, and source term rates) in batch and semibatch, constant-composition crystallization systems. Of the four differential techniques tested, the methods of Bramley et al. (J. Colloid Interface Sci. 1996, 183, 155-165) and Livk et al, (AIChE J. 1999, 45 (7), 1593-1596) were, the most,accurate. Comparisons of experimental and predicted crystal size distributions showed that the kinetics estimates obtained by the integral method lead to better agreement with the experimental data than those obtained by the differential methods, The integral and differential techniques both give similar estimates of the crystal growth rate but deviate more in the case of agglomeration and source term rates. Overall, the uncertainties of the kinetics estimates obtained by the integral and differential methods were of comparable magnitudes.