In short-fiber reinforced composites, it is widely accepted that the fiber orientation plays an important role on their overall physical and thermo mechanical properties. To predict the properties of such composite materials, a full 3D fiber orientation characterization is required. A variety of destructive and nondestructive techniques have been developed, but all the methods have the same common point that they are very tedious and time consuming. Knowing that the fiber orientation induced by the flow remains mainly in the flow plane, an easier method has been performed for injection molded fiber-filled polymers. It is based on the simple 2D SEM image analysis of a specific 45 degrees-oblique section plane. Then, the indetermination of fiber orientation from an ellipse mark analysis does not exist anymore. This novelty also turns out to be much more accurate. To achieve measurements over large composite samples, the method has been fully automated. POLYM. ENG. SCI., 48:2159-2168, 2008. (C) 2008 Society of Plastics Engineers