The development of a Population Balance Model (PBM) for a pharmaceutical granule drying process requires a continuous growth term; the latter actually represents the drying process as the moisture content is the internal coordinate of the PBM. To establish such a PBM, a complex drying model for a single granule needs reduction in complexity. The starting point is a detailed model that describes the drying behavior of single pharmaceutical granules. A Global Sensitivity Analysis (GSA) was performed to detect the most sensitive degrees of freedom in the model as these need to be retained in the reduced model. Simulations of the complex drying model were, in a next phase, used to develop the reduced model, which describes the decrease of the moisture content in function of the gas temperature. The developed reduced model was then included in a Population Balance Equation (PBE) to describe the drying behavior of a population of granules. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 1127-1138, 2013