By using X-ray micro-computed tomography it was possible to determine the extent of agglomerate breakdown during the mixing and extrusion of ceramic pastes. The technique allowed a significant improvement over previous attempts to visually monitor agglomerate breakdown which have been hampered by the lack of a suitable technique with which to obtain fast and reliable three-dimensional data regarding the volume and size distribution of agglomerates. The extent of agglomerate breakdown in a model agglomerate/matrix system was compared after processing by z-blade mixing followed by ram extrusion and by a co-rotating twin-screw mixing/extrusion process at various operating parameters; the latter process was found to be more effective at breaking down the agglomerates under all processing conditions. (c) 2007 Elsevier Ltd. All rights reserved.