Introduction: The upper airways (UA) are the main entrance into the human body. They present a large surface of covering mucous epithelium to form a physical barrier against infectious agents, environmental irritants, etc. There are important immune mechanisms in this area either specific or nonspecific. Aim: To present the current knowledge about the immune mechanisms of the UA mucosa, including a review about the function of Lymphatic Waldeyer’s Ring (LWR) and the effects of adenotonsillectomy on immune function. Methods: Review of papers catalogued in both Medline and Lilacs databasis. Conclusions: Non-specific immunological mechanisms (as mucous enzymes, mucociliary transportation, cough reflex, etc) contribute to the defense of the UA yet in infants. Specific mechanisms involve inflammatory mediators and lead to antigenic memory. Tonsils, present important anatomical and functional differences if compared to other lymphoid organs. Antibodies production in tonsils - including secretory IgA - is crucial to the individual immunological competence. The number of adenotonsillectomies has decreased since the 60’s decade, under the lights of the Immunology advances. Facing the persistent controversies in the indication of adenotonsillectomy, an immunological evaluation is recommended in the pre-operative period, as well as good sense in assisting each patient.