The influence of obstructed nasal passages was investigated in l4 patients with allergic rhinitis. Disordered breathing in sleep was found in all patients in the form of periodic breathing, and hypopneic and hyperpneic episodes, associated with characteristic "microarousals' from sleep. Patients had an average of 50 "microarousals' from sleep, ten times more than normal controls. It is suggested that increased upper airway resistance and increased nasal discharge are responsible for the disordered breathing in sleep and for the "microarousals'.