To prospectively evaluate the effects of adenotonsillectomy (T&A) for sleep disordered breathing (SDB) on asthma outcomes as compared with control asthmatics who did not have a T&A.Children aged 4 to 11 years with asthma who underwent T&A for SDB (n = 80) were included. Control patients with asthma (n = 62) were recruited from clinical office visits and did not have clinical SDB and/or polysomnography as indications for T&A. Control patients were matched to the study patients on the basis of age within 1 year, sex, and Asthma Severity Classification. SDB was based on overnight polysomnography and/or clinical assessment of nighttime symptoms of snoring and breathing difficulties, daytime symptoms, physical examination findings, and the Clinical Assessment Score-15, a tool for diagnosing SDB. Asthma was diagnosed and managed by a pediatric pulmonology specialist or a pediatrician on the basis of clinical history, pertinent family history, response to medications, pulmonary function tests, and the exclusion of other diagnoses.Asthma Severity Classification was determined by chart review and was classified on the basis of the National Heart, Lung, and Blood Institute guidelines. Asthma clinical outcomes, including the number of asthma exacerbations, frequency of systemic steroid use, number of emergency department visits for asthma, and number of hospitalizations for asthma in the previous 6 months were assessed. Childhood Asthma Control Test (C-ACT), the primary outcome measure, and Pediatric Sleep Questionnaire (PSQ) scores were obtained at study entry and at 6 months after surgery or enrollment.Subjects had a mean age of 6.8 years, at least 60% were boys, the majority were black, and most had intermittent or mild persistent asthma. T&A subjects were more likely obese (45% vs 34%). Asthma exacerbations and emergency department visits were improved for both groups, steroid use was improved in only the T&A group, and hospitalizations were improved only in the controls. However, the frequency of all these events at entry and follow-up were low for both groups. Mean C-ACT scores were similar at entry (T&A = 21.86, control = 22.42) but significantly different at follow-up (T&A = 25.15, control = 23.59) and overall significantly improved for both groups at follow-up. Mean PSQ scores significantly improved (T&A = 0.14, control = 0.17) for both groups at 6 months. Baseline PSQ and study group assignment were the main predictors of change in the C-ACT.Treatment of SDB significantly improved C-ACT and PSQ scores. Asthma clinical outcomes were slightly improved but were already not occurring often at baseline.Although ethical constraints preclude comparing T&A versus no T&A in children with SDB, this supports other studies that show that T&A improves asthma. Interestingly, the controls also had improvement in their mean C-ACT and PSQ scores without any intervention. Limitations include that the sample size was not large enough to assess how T&A really would have affected asthma clinical outcomes and that most of the subjects had intermittent or mild persistent asthma at baseline, so it is unknown how these findings would apply to patients with moderate or severe asthma.