We are in the throes of building and testing an expert system whose goal is to detect major changes in authors’ voices in a collaboratively written document. We are studying the elements of style for markers that would indicate that one author differs from another. Our goal is not to automatically edit the document to make it once voice. There are cases in academic writing, for example, where the voice is supposed to change, like the introduction and conclusion to a paper is written in a different style than the method and results sections. But there are clearly cases where the authors would like to achieve one voice. One author may use longer sentences and connect ideas with semicolons, where the other author has shorter sentences and uses connectors like “thus” and “however.” Our job is to detect major changes paragraph by paragraph and to alert the authors to the existing differences, not just telling them that there is a difference but in what aspect.