A particle image probe comprising a CCD camera and an image processing system has been developed for on-line monitoring of granule size distribution and shape in a fluidized bed granulation. Continuous granule measurements by the image probe were digitized and processed by the image processing system, and granule size distribution and shape were computed in real time. The developed system was applied to the monitoring of granule growth in pharmaceutical granulation and its validity was confirmed. Application of this system to the dynamic control of granule size and shape was also demonstrated.