The behavior of a commercial short glass fiber filled polypropylene has been studied. It is well known that a thermoplastic polymer filled with short fibers with an initial isotropic orientation state exhibits a viscosity overshoot when sheared in the parallel plate geometry of a rheometer in the molten state. In this work, following a first deformation, the sample has been sheared in the reverse direction and a small viscosity overshoot has been measured. Similarly under stress growth experiments a large normal stress overshoot was observed. When the flow was reversed the normal stresses were initially negative and then exhibited a small positive overshoot. A model has been used to simulate these viscosity and normal stress overshoots. It is based on the Folgar-Tucker equation for fiber motion and the Lipscomb constitutive equation. This equation has been empirically modified to correctly predict the overshoots. (C) 2004 Elsevier B.V. All rights reserved.