In this work, the experimental design methodology is applied to optimise MgO production from magnesium sulphate salt. This is a two-step process through an intermediate product (Brucite: Mg(OH)2). For the first step, a fractional factorial design and a centred composite one are used in order to establish appropriate experimental conditions for Mg(OH)2 obtention. The most favourable conditions for the second step to obtain MgO were determined using only a fractional factorial design. The decomposition of the optimal precipitated Mg(OH)2 was analysed by DTA/TGA and the crystallisation process was observed by XRD. The morphological properties of the MgO agglomerates were examined by SEM. Copyright © 2010 John Wiley & Sons, Ltd.