The acoustics of the Ancient Theatre of Beneventum has been object of attention by the authors since five years ago when measurements were carried out in the aim of its characterization in the present state. This theatre was built by Emperor Hadrian in the 1st century A.D. Later, historical events as barbarian invasions, earthquakes and floods determined its abandonment. A large part of the materials of the construction was used to build defensive walls in the Lombard period and for the embellishment of churches and palaces. During the course of subsequent centuries the theatre became the settlement of humble dwellings. At the start of the 20th century the crumbling houses were demolished to start the reconstruction of the theatre which was completed, as it appears in the present state, in 1950. This paper reports a computer simulation of the acoustics of the Roman Theatre performed by Odeon software. Calculated results are compared with those stemmed from the previous measurements carried out by the authors in the unoccupied theatre. Furthermore, a simulation of the effects of audience occupation on the acoustics is presented.