In all the history of hand-written books, one of the most distinctive and handsome scripts is that of the abbey of Monte Cassino. This study examines for the first time in detail the development of this script during the Abbey's greatest period of wealth and influence, under Desiderius (abbot 1058-1087) and his successor Oderisius (abbot 1087-1105). The characteristic Cassinese hand was established long before, but in this period it was transformed into what is today considered its classic form. The present study rests on a fresh examination of many details of the Beneventan (South Italian) script in aspects incompletely studied before. It aims to provide a new history of Monte Cassino as a writing centre and to offer a context for many unique or valuable texts manuscripts that it processed.