Congenital central hypoventilation syndrome (CCHS) is associated with hypoventilation during sleep, but breathing can be adequate during wakefulness. It has been assumed that in awake CCHS patients breathing is activated by the forebrain, even voluntarily (i.e. Ondine's Curse). We tested whether or not an abnormal breathing pattern can be provoked by intense mental concentration in CCHS patients as this would be expected to disturb any voluntary control over breathing if present. Breathing (inductance plethysmography), end-tidal PCO2) (PETCO2), arterial oxygen saturation (SaO2) and EEG were measured in 5 children with CCHS (aged 8-17 years) and 5 controls during 5 min periods while resting; reading; performing mental arithmetic and playing a hand-held "Nintendo" game. There were no significant differences between controls and CCHS (unpaired t-tests, P > 0.05) in mean breath duration, tidal volume, ventilation, SaO2 or PETCO2 during REST or the conditions of mental stimulation. Both groups increased ventilation during mental stimulation. Respiratory variability was not greater in CCHS in any condition. These data provide indirect evidence that CCHS patients do not require voluntary activation of every breath (they do not have Ondine's Curse) and suggest that mental concentration might stimulate the respiratory complex as part of a generalised CNS arousal.