My paper on developing LanguageTool , focused mostly on new features needed to support many different languages in LT, has just been published in Software - Practice and Experience (if you have no access to SPE, here is the final uncorrected draft ). The paper contains a section with empirical results - I tested LanguageTool on Polish, and compared the results with Microsoft Word grammar checker (the only one that exists for Polish beside LanguageTool). The results are pretty good - whereas LanguageTool rules seem to create few false alarms (the precision level is around 90% for most test samples), MS Word tends to have a lot of them (the precision level is in best cases around 50%, and in many cases even lower). Sample text MS Word matches MS Word precision LT matches LT precision Frequency Dictionary Corpus 4572 22,00% 8552 92,00% Camera-ready book 58...