Near-infrared (NIR) spectroscopy has been extensively applied for a non-destructive quantitative analysis in biomedical and chemical industry [1].With the advent of US FDAs new initiative,"Pharmaceutical CGMPs for the 21st century",process analytical technology (PAT) has emerged as one of the key elements for QbD (quality-by-design).In this study,the film thickness of pharmaceutical pellets was examined during a fluid-bed coating process using in-line NIR.The precise monitoring and prediction of film coating thickness with appropriate control strategy is crucial to the overall quality assurance of coated solid dosage forms including dissolution characteristics [2].Pharmaceutical pellets of a test formulation were manufactured and coated in a fluid-bed by spraying the hydroxypropyl methylcellulose (HPMC) coating solution.NIR spectra acquired in 4000-14000 cm-1 region via a fiber-optic probe were recorded during coating process for the consequent analysis.Actual coating thickness of pellets was determined using not only a confocal laser scanning microscopy (CLSM) but a laser diffraction particle size analyzer (LD-PSA).The correlation between NIR spectra and analysis data of sampled pellets was evaluated and the coating thickness was predicted through partial least squares (PLS) calibration model.As a result,determination coefficient (R2) values using CLSM and LD-PSA for reference data analysis methods were 0.9984 and 0.9961,respectively.In addition,a prediction coating experiment for 70 minutes demonstrated that the end-point can be accurately designated via NIR in-line monitoring with appropriate calibration models.Conclusively,our approach can be implemented as an effective PAT tool for fluid-bed pellet coating processes.Detailed data will be presented for intense discussions.