Reaction-bonded Si3N4 toughened by oriented SiC platelets was fabricated via low pressure injection moulding (LPIM). Initially, the rheology of ceramic suspensions was optimized with respect to solid content, SIC platelet loading, particle surface properties and binder composition. Surface active additives were used to modify the particle-polymeric binder interphase in order to prevent particle reagglomeration, to reduce the viscosity and/or to increase the solid content. The relationship between LPIM processing variables and platelet orientation in injection moulded reaction bonded silicon nitride ceramics was studied and the resultant mechanical properties were compared to composites containing randomly dispersed platelets.