A night-time polygraphic sleep recording with continuous HbSaO2 monitoring was performed in 11 chair-bound Duchenne muscular dystrophy patients with severe restrictive lung disease but with blood gas values within normal limits when awake. No abnormalities of sleep pattern were detected. Nocturnal sleep did not have significant adverse effects on respiration. However, in 6 patients, infrequent central apnoeas or hypopnoeas occurred which were associated with falls in HbSaO2 greater than those that have been reported to be in normal subjects. The magnitude of HbSaO2 falls appeared to be significantly correlated with functional residual capacity values. Overall, the findings revealed a relatively preserved, although unstable, blood O2 balance during nocturnal NREM and REM sleep in patients with Duchenne muscular dystrophy, even in an advanced stage of their illness.