Terahertz　in-line　sensing　was　successfully　demonstrated　previously　for　measuring　the　coating　thickness　of　individual　pharmaceutical　tablets　during　a　production　scale　film　coating　process.　This　paper　investigates　how　this　technology　can　be　used　to　evaluate　the　impact　of　changes　in　the　process　conditions　on　the　inter-tablet　coating　thickness　distribution.　The　process　changes　that　were　investigated　in　this　study　were　the　removal　of　the　mixing　baffles　from　the　coating　pan,　blockage　of　one　of　the　spray　guns　and　the　addition　of　uncoated　tablet　cores　to　a　bed　of　partially　coated　tablets.　Using　the　terahertz　sensor　the　coating　thickness　of　more　than　20　individual　tablets　was　sampled　per　minute　in　situ　throughout　the　coating　process.　By　analysing　the　resulting　variation　in　coating　thickness　distribution　it　was　possible　to　resolve　the　effect　of　all　these　process　changes　on　the　coating　thickness　homogeneity　within　the　batch.　©　2013　IEEE.