Computer simulations of granular materials are often based on the Distinct Element Method (DEM) where each grain is considered individually. Since large quantities of grains are required to perform realistic experiments, high performance computing is mandatory. This paper presents the basis of the DEM, a sequential algorithm for spherical grains in 3D and the adaptations to obtain a parallel version of that algorithm. Visualization is also discussed, as the drawing and animation of large sets of grains require special techniques and state-of-the-art graphics hardware. Finally, some applications are presented.