High-quality magnesium hydroxide powders can be produced by hydrating slow-reacting magnesia in dilute magnesium acetate solutions. The kinetics of this process are very crucial for process design and control, and for the production of a powder with desirable particle morphology. In this work, industrial heavily-burned magnesia powders were hydrated in 0.01-0.1 mol dm(-3) magnesium acetate solutions at temperatures ranging between 333 and 363 K, Examination of the magnesium hydroxide produced and the analysis of the kinetic data suggest that the hydration of heavily burned magnesia in magnesium acetate solutions is a dissolution-precipitation process controlled by the dissolution of magnesia particles. The activation energy was estimated to be 60 kJ mol(-1), while the reaction order with respect to acetate concentration was found to be about one.