The rheology properties of aluminum composite mixes fro powder injection molding (PIM) were analyzed. The viscosity of the composite mixes decreased with increases in the shear rate range required for PIM. It was found that molding temperatures within a range of 200°C-225°C did not affect the viscosity of the composite mixes. The results show that the rheological properties provide quantitative guidelines in the prediction of fiber orientation in metal matrix composites produced by PIM.