In the pharmaceutical industry, more than half of all tablets receive a film coating. A commonly used technique is drum coating, where a film solution is applied to the moving tablets by a spray nozzle. Important process parameters include the amount and temperature of drying air, as well as spray nozzle position. Among other influences, the proper adjustment of these parameters has a great impact on spray loss, defined as the fraction of spray liquid that does not form a film on the tablets. Often, the lack of scientific data hinders a process setup based on engineering principles, resulting in operational conditions based on trial-and-error approaches. Here, we show how a coating system can be numerically modeled by means of computational fluid dynamics (CFD) techniques. Furthermore, we present how different parameters affect the efficiency of the process, leading to a deeper understanding of the coating device. (C) 2011 American Institute of Chemical Engineers AIChE J, 58: 399-411, 2012