In this study, the first study made of the editing practices of professional editors, 51 editors on the Iowa State University campus were asked to edit a problematical one-page journalistic newsletter article. The changes they indicated in their samples were analyzed according to the operations of addition, substitution, deletion, transferring, paragraphing, and zero markings per line. These operations corresponded to the maxims of Grice's Cooperative Principle of the Speech Act Theory (Grice, 1975, pp. 41-59). The motivations for the various editorial changes were hypothesized. The copyeditors' overall patterns were categorized by type according to Buehler's editing schemata (Carosso, 1986, p. 20). It was noted that, unlike student writers, professional editors tend to use all the operations and value quantity, quality, manner, and relation almost equally. In addition, they tend to look at writing holistically, editing substantively and changing order or format to fit the conventions of the piece.