The shape of standard round tablet was represented by using the intersection of three spherical surfaces. Using this model, the contact criteria for tablet-flat surface and tablet-tablet contact were developed and were applied for tablet-tablet contact using a DEM simulation implemented in Matlab (TM) code. In addition, a high-speed digital imaging system was used to capture the images of one tablet hitting another fixed tablet anchored to a flat surface. Comparison of angular velocity showed good agreement between simulation and experimental results. The simulations were compared with alternative multi-sphere representations for the shape of the tablet and the results showed that the simulation times for 66- and 178-sphere representations were much larger than that for the tablet simulations. In addition, the simulation results for all the multi-sphere representations were significantly different from those of the tablet simulation. (c) 2005 Elsevier B.V. All rights reserved.