In severely handicapped patients, chronic respiratory insufficiencies and recurrent hypoxemia especially during sleep are one of the major problems to take care of them. To clarify the pathophysiology of respiratory disorders during sleep, we examined 5 severely handicapped patients with no respiratory distress during wakefulness, but with signs of latent respiratory insufficiency by means of polygraphical all-night study including the arterial oxygen saturation (SaO2) monitoring. In the severely handicapped patients, sleep hypoxemia occurred frequently. The value of SaO2 decreased in proportion to the intensity of apnea determined by polygraph. The relationship between the value of SaO2 and sleep stage was variable in each patient. Four patients had mainly obstructive respiratory disorders and one had a central type respiratory disorder. The density of REM stage decreased in the obstructive type. In the central type, the repeat of REM stage with normal REM density was not observed. In one patient with obstructive type and one with central type, hypoxemia was improved with an increased number of REM stage by O2 inhalation.