The authors review 561 patients suffering from odontogenic abscesses and phlegmons which were large enough to merit hospitalisation in the Division of Maxillo-Facial Surgery of the Odontostomatological Clinic at the University of Turin during the period from 1972 to 1990. The main features of these septic processes are evaluated: site, size, mode of growth and evolution, tooth responsible. Special attention is paid to the treatment performed: this was essentially based on antibiotic therapy and/or drainage of the abscess via a transcutaneous, transmucous or transdental route. The need to combine medical therapy with surgical drainage of purulent material was noted in the treatment of large infections; in many cases medical therapy alone was unable to guarantee the resolution of the pathology; on the other hand, surgical drainage alone in some cases led to the patient's recovery.