Two phase ceramic filaments have been made by the co-extrusion of different green mono-filaments, each extruded mono-phase being produced from two differing material sources. The first was based on sol technology and the second based on oxide ceramic powder (+ thermoplastic binder) processing. Initially, mono-phase filaments were produced and re-extruded to produce bi-phase filaments which were then sintered to produce ceramics with aligned fine microstructures. The scale and fineness of the final sintered structure and the orientation of the g-rains in each phase (alumina or zirconia) have been determined by SEM and TEM and have been found to depend on the type of original precursor used, the powder grain size added and the temperature of heat treatment chosen. The study seems to demonstrate the viability of this novel multiple sol-gel based extrusion process to obtain optimised engineering structures for use at high temperatures. (C) 2003 Elsevier Ltd. All rights reserved.