The immunodeficiency in ataxia-telangiectasia (A-T) is highly variable. Laboratory abnormalities correlate poorly with susceptibility to infection and are almost exclusively restricted to patients with mutations resulting in no A-T mutated kinase activity. Opportunistic infections are unusual but sinopulmonary infections are common and can contribute to the development of pulmonary insufficiency. Preventing lung disease involves maximizing immunity, as well as measures to counteract the tendency to develop pulmonary aspiration, which increases with age. Immunizations should include pneumococcal conjugate, influenza and, in all but the most severely lymphopenic, measles, mumps, rubella, and varicella zoster vaccines. Prophylactic azithromycin is commonly used and believed to be useful, although a firm evidence base for its use in A-T is lacking. Approximately 12-15% of patients require regular immunoglobulin therapy. Further studies are required on potential disease-modulating therapies, such as antioxidants and corticosteroids. Strategies for the modulation of gene transcription remain at the preclinical laboratory stage.