Fifteen manuscripts preserve a treatise attributed to William of Moerbeke under the title of Geomantia. This text bears an intriguing and complex testimony to the geomantic science in the Middle Ages. Although it was first examined by Thérèse Charmasson, no critical edition is currently available. The pages focus on the first critical edition of the text, and contain a documentation of the results, based on a philological analysis conducted on 15 manuscript witnesses. Moreover, they present a strategy of the text edition, currently in progress. The critical edition is part of the project FIRB 2012 Foreseeing Events and Dominating Nature: Models of Operative Rationality and the Circulation of Knowledge in the Arab, Hebrew and Latin Middle Ages, (unit Lecce, directed by Alessandra Beccarisi).