Simultaneous orifice and capillary rheometry at 160degreesC was used to determine flow parameters of aluminum nitride extrudates plasticized with a polyethylene-mineral-oil binder. Data were analyzed using the Benbow model for square-entry ram extrusion. Variables included the powder concentration, polymer molecular weight and concentration, and lubricant concentration. Die-entry rheology was explained in terms of the mean interparticle separation, polymer spatial requirements, and lubricant adsorption. Particles and polymer were observed to not pack independently. The yield stress of the body increased rapidly as the solids loading approached the critical volume limit of extrudability. An increase in polymer molecular weight or partial decrease of adsorbed lubricant increased the yield stress of the body and produced a satisfactory extrudate.