Five adult subjects with severe kyphoscoliosis were monitored during sleep. Several types of breathing abnormalities, including obstructive apnea and hypopnea, were noted. The lowest oxygen desaturations occurred during rapid eye movement (REM) sleep. Arterial pressure, continuously measured in one subject, progressively increased throughout the night in association with abnormal breathing. The use of a cuirass ventilator did not improve the nocturnal problem.