Giovanni Battista Rasario was a well-known physician and translator of Greek classical texts of the Renaissance. In 1562–1563, he edited Galen's Opera omnia, printed by Valgrisi in Venice. This edition is remarkable because of the order of Galen's works, its new translations and also its forgeries. As the preface indicates, other scholars and physicians collaborated with him on this edition. This essay investigates the philological and historical issues of Rasario's edition through an analysis of its preface as well as the dedication letter. Both are rich sources of information on the work accomplished by Rasario, and also bring to light the hitherto unknown relationship between him and his collaborators.