The damage and deformation behaviour of particulate reinforced metal matrix composites (PMMCs) can be highly sensitive to local variations in spatial distribution of reinforcement particles, which markedly depend on melt processing and solidification stages during production of PMMCs. The present paper attempts to study the effect of solidification rate on cluster formation in an Al-Si-Mg (A356) alloy composite reinforced with SiC particles and to explore the applicability of spatial functions to PMMC microstructures to quantify the degree of clustering The observed amount of clustering in composites was evaulated with the nearest neighbour and local density statistics in terms of variations in dendrite arm spacings and solid fractions at the dendrite coherencies. The results indicate that the distribution of SiC particles is controlled by the secondary dendrite arms. Depending on dendrite arm spacings and particle content, clustering is most pronounced at distance scales ranging approximately between 150 and 500 mu m, which is much larger as compared to the nearest neighbour distances. (c) 2007 Elsevier B.V. All rights reserved.