The diagnosis of quinsy is traditionally established on the basis of clinical observations and sometimes several diagnostic punctures. The present study has focused on the possible usefulness of intraoral ultrasonography (IOU) as a diagnostic tool when a peritonsillar abscess is suspected. The results show that it is possible to demonstrate, with a high degree of accuracy, the presence of an abscess, its volume, location, and its relation to the carotid artery. With this information an exact and safe diagnostic puncture can be performed when necessary and avoided in cases with clinical signs of quinsy with no abscess.