OBJECTIVETo evaluate the safety and efficacy of in-office, temperature-controlled radiofrequency submucosal tissue volume reduction using the Somnoplasty procedure for the treatment of symptomatic chronic obstructive tonsillar hypertrophy.DESIGNA prospective, nonrandomized, 3-phase protocol using in vitro and in vivo studies associated with operative tonsillectomy and clinical procedures performed in-office.SETTINGHospital operating room and private practice otolaryngology office.STUDY POPULATIONIn vitro studies of 14 tonsil specimens following tonsillectomy; in vivo studies of 11 tonsils before tonsillectomy; and clinical procedures performed on 9 adults, ages 24 to 47 years, with symptomatic chronic tonsillar hypertrophy.OUTCOME MEASURESFor phase 1, histologic tissue sections; for phase 2, histologic tissue sections and clinician and patient questionnaires regarding procedure morbidity; and for phase 3, measurements of oropharyngeal airway size and clinician and patient questionnaires regarding procedure morbidity and symptom improvement.RESULTSA 2-needle radiofrequency probe ablated tonsil stromal tissue while leaving overlying mucosa and underlying structures intact. On average, oropharyngeal airway was enlarged 12 mm, with a 70.8% calculated reduction in tonsil size. Procedures were well tolerated and had only minimal pain and dysphagia. There were no episodes of hemorrhage, and patients resumed normal activity within 1 to 2 days. Substantial improvement was reported in daytime sleepiness, snoring, voice clarity, swallowing, and throat irritation.CONCLUSIONSTemperature-controlled radiofrequency submucosal tissue volume reduction is a safe and effective method of treating symptomatic obstructive tonsillar hypertrophy. It is well tolerated by the patient under local anesthesia in the physician's office and has minimal postprocedure pain and dysphagia, with rapid return to normal activity. The procedure reduces tonsil size and increases airway size, leading to a reduction in symptoms.