Peritonsillar abscess occurs when bacterial infection of the tonsil spreads to the potential peritonsillar space deep around the tonsil, in patients with recurrent tonsillitis or in those with chronic tonsillitis who have been treated inadequately. Peritonsillar abscess, in spite of decreasing incidence substantially since the advent of antibiotic therapy, is not rarely experienced in the clinical field. The diagnosis of peritonsillar abscess is traditionally established on the basis of clinical observation and sometimes several diagnostic punctures. But diagnostic puncture is painful for the patients and usually impossible to perform in children without the use of general anestheisa. The present study has focused on the possible usefulness of ultrasonography as a diagnostic tool and on the camparison of the superiority between intraoral ultrasonography and external neck ultrasonogrphy when a peritonsillar abscess is suspected. The results show that intraoral ultrasonography is a better diagnostic tool, with a higher degree of accuracy, in the presence of abscess, its volume, location, and its relation to the carotid artery rather than external neck ultrasonography.