Most adolescents with ataxia telangiectasia (A-T) develop progressive bulbar muscle weakness and decreased pulmonary reserve. The purpose of this study was to define the patterns of sleep and respiration during sleep, and to identify sleep-related breathing problems in subjects with A-T. To address these issues, overnight polysomnography was performed on 12 adolescents with A-T. Eleven of the 12 subjects completed overnight polysomnography. The median age was 16 years (range, 13-20 years). All subjects in the study were wheelchair-bound and the median forced vital capacity (% predicted of normal) was 44% (range, 16-82%). The mean sleep efficiency was 72.6% with a mean apnea hypopnea index (AHI) of 0.7 events/hr (range, 0-2.2). The majority of apnea/hypopneas were REM related. The mean central apnea index was 0.1 events/hr (range, 0-0.2). The mean oxygen saturation nadir was 92.7% (range, 87-96) and the mean peak end-tidal carbon dioxide ET(CO(2) ) value was 53.8 mm Hg (range, 49-60). Two of 11 subjects had ET(CO(2) ) values >or=50 mm Hg for more than 50% of total sleep time. In this study, the majority of A-T adolescents had infrequent partial or complete upper airway obstructions during sleep and minimal nighttime hypoxemia. They did, however, have decreased sleep efficiency most likely, due in part, to their underlying neurological condition. This decrease in total sleep time may underestimate hypoventilation. Based on these findings, overnight polysomnography should be considered in adolescents with A-T, particularly in those in which there is a clinical suspicion of sleep related breathing abnormalities.