Sleep is associated with moderate or severe arterial desaturation in many disease states. This study was undertaken to evaluate whether hypoxemia during sleep was a significant problem in the spinal cord injured patient. Eleven patients with cervical or thoracic cord injury who had significant respiratory deficiency were evaluated. The mean age was 29.2 +/- 14. Vital capacity (VC) for the group revealed a mean of 43.1 +/- 18.1% of predicted, inspiratory capacity (IC) was 51.6 +/- 20.2% of predicted, and expiratory reserve volume (ERV) was 23.6 +/- 24.7% of predicted. In eight patients blood gases revealed a mean PO2 of 81.5 +/- 8.4 mmHg and PCO2 of 38.9 +/- 3.4 mmHg. Sleep screening studies were done using the Hewlett-Packard ear oximeter. They were studied for a mean of 2.6 +/- 1.1 hours. The initial O2 saturation was 96.6 +/- 1.6% and dropped to a mean of 90.6 +/- 6.4%. Only 1/11 reached saturation to less than 85% and 2/11 reached levels lower than 90%. Only age was significantly correlated with amount of desaturation (p less than .01). The level of the lesion, and % predicted ERV were not. One of the two patients who had hypoxemia with sleep had unilateral diaphragmatic paralysis. It is concluded that young quadriplegic patients with normal diaphragmatic function have no severe desaturation during sleep, but older patients and patients with some diaphragmatic dysfunction should be screened for sleep desaturation.