The dissolution kinetics of pure gibbsite in concentrated sodium hydroxide solutions was studied. The experiments were performed under ambient pressure and at 60-85 degrees C. The changes in morphology of the solid phase were studied during the reaction by particle size, porosity, and surface area measurements as well as scanning electron microscopy. Reaction rates were observed to be strongly dependent on temperature and hydroxide concentration. Several kinetic models, based on different representation of the surface area of gibbsite, were compared to the experimental data and a good correlation between a model incorporating rough/porous geometry and the experimental data was obtained.