The modeling of the transient behavior of the crystal size distribution is essential to predict and effectively control the quality of the end product. The population balance approach provides an appropriate mathematical framework for the modeling of crystal size. For most batch crystallization processes, it is often difficult to obtain on-line relevant information about the crystal size distribution and the dissolved solid concentration in the liquid phase. We have recently developed an automated image analysis strategy that yields real-time measurements of both particle length and width with acceptable accuracy. In this contribution, we present an approach for validation of a population balance model for batch crystallization of monosodium glutamate by using on-line information about the state of the crystallization process provided by our image analysis strategy and other in-situ process analytical tools such ATR-FTIR. © 2009 Elsevier B.V. All rights reserved.