This study was conducted to determine the possibility of using an intracavitary ultrasound probe to differentiate between peritonsillar cellulitis and peritonsillar abscesses. Three volunteers and 11 of 12 patients were successfully scanned. The ultrasound method successfully demonstrated four cases of peritonsillar cellulitis and seven cases of peritonsillar abscesses. We conclude that ultrasound is a simple, safe, and noninvasive method of both assessing unilateral tonsillar swelling and determining the presence or absence of peritonsillar abscess.