The direct pelletization process is a fast and flexible operation with the potential to produce high quality particles appropriate for sophisticated oral solid dose formulations where a narrow particle size distribution is required. Traditional methods are too slow or subjective and therefore may be an unacceptable risk for use as an in-process control in a control strategy. An at-line direct imaging method with automated high-speed image analysis can be practically used during processing to accurately predict the process end-point with fast objective PSD data, supported by particle images, to significantly improve process optimisation and control.