The initial fill and the subsequent discharge of containers containing granular material have been modeled using the discrete element method (DEM). In particular, the behavior of granular material in three dimensions is accounted for. The aim is to study the distributions of normal wall forces and pressures developed at the end of filling process (static state) and those developed during outflow from the containers (dynamic state). A hopper, a silo with a hopper bottom, and a flat-bottomed silo have been chosen for DE analysis. The granular material is modeled as a particle assembly consisting of mono-sized, spherical, coliesionless particles. Movement of individual particles during the outflow caused by gravity was also studied. The simulation results obtained in the present work are realistic and show clearly the advantages of DEM to understand the complex flow behavior of granular materials. (c) 2005 Elsevier B.V. All fights reserved.