Adenoids, or pharyngeal tonsils, are folds of lymphatic tissue covered by ciliated epithelium. They are found in the roof and posterior wall of the nasopharynx at the back of the throat behind the uvula.

Adenoids are part of the immune system as they trap inhaled viruses and produce antibodies, particularly in children. This function decreases with age as the adenoids shrink. Because of this, the problems caused by enlarged adenoids rarely occur in adults.

The condition where hypertrophy of the pharyngeal tonsils occurs is also referred to as adenoids. Enlarged adenoids can obstruct breathing through the nose, and it is common when this happens for them to be surgically removed in a procedure called adenoidectomy. This procedure is carried out through the mouth under a general anaesthetic and involves the adenoids being curetted or cauterised. Sleep apnoea, recurrent infection of the adenoids or distorted speech are also reasons for adenoidectomy. The procedure is often carried out at the same time as a tonsillectomy. Adenoidectomy is also carried in patients who have chronic ear infections caused by the adenoids blocking the eustachian tube.