Since Jerome's Latin translation of the monastic rules attributed to Pachomius (287-347) these have never vanished from the memory and the tradition of Western monasticism. This contrasts strongly with a cluster of rules written in Coptic. These were not published until the 19th century, and in accordance with the edition of Louis-Théophile Lefort they are usually called the 'règlements' (regulations) of Horsiese. This attribution has, however, been questioned. The present article aims to offer a sound basis for the view that Horsiese is indeed the author of these rules.