A numerical technique is proposed for the simulation of cavity filling process during injection molding of glass-bead filled polypropylene. The mold cavity is of cylindrical shape. Marker And Cell (MAC) method is utilized for solving the transient flow phenomena, after a mathematical simulation of the flow model is carried out by using the relevant continuity and-momentum equations governing the system. The complexity of the equations involved, results in the simplifying assumption of incompressible and isothermal flow process. A computer program is written on the basis of finite-difference equations developed during the application of MAC method under the prevailing conditions. The numerical results yield significant data on the progression of the melt front, the velocity profiles in both axial and transverse directions and the pressure distributions at different times and positions in the cavity.