The objective of this work is to determine the influence of the agglomeration state of the MA mixture on the microstructure and the chemical composition of SPS end-products. In order to produce MoSi2 with a microstructure and a density perfectly controlled via reactive sintering implying an SHS reaction, the characteristics of Mo/Si mechanically activated (MA) powder mixtures were investigated. Indeed, the MA powders have been characterized in terms of their surface specific area, size, phase composition and microstructure. The high-energy milling allows the formation of agglomerates (0.8 to 800 gm) composed of nanometric crystallites of molybdenum and silicon, as a consequence of a continuous fracture-welding process. This enhances the reactivity of powder mixtures due to an increase of interface number. The simultaneous synthesis-consolidation in one step could be performed using the spark plasma sintering (SPS) process. This study was performed on three agglomerate sizes: empty set < 125 mu m, <= 125 mu m < 250 mu m and >= 250 mu m. (C) 2010 Elsevier B.V. All rights reserved.