We hypothesized that withdrawal of nasal continuous positive airway pressure (CPAP) in patients with sleep apnea would produce a measurable stress response. To test this hypothesis, we ceased CPAP in eight patients regularly using nasal CPAP long term and measured the effect on sleep apnea as well as plasma and urinary levels of the stress hormones, noradrenaline, cortisol and adrenocorticotropic hormone (ACTH). CPAP withdrawal led to an immediate recurrence of sleep apnea with increases in apnea index, arousal index and oxygen desaturation (all p < .0001) but no change in levels of noradrenaline, cortisol or ACTH. We conclude that acute withdrawal of CPAP in patients with sleep apnea does not lead to a classic stress response.