We treated an infant with congenital central hypoventilation syndrome ("Ondine's curse"). She was cyanotic and given ventilatory support at the first hour after birth. An investigation of sleep state and respiration performed at the age of 3 months led to this diagnosis. Hypoventilation persisted in all sleep stages, with the most severely reduced tidal volumes occurring during delta-wave sleep (stages 3 and 4). In addition, severe secondary reduction in tidal volumes occurred in sleep-onset REM sleep. This phenomenon was absent in non sleep-onset REM sleep. At 4 months of age, her respiratory treatment was successfully converted to positive-pressure ventilation via a nasal mask, thus avoiding tracheotomy. This transition to noninvasive ventilatory support dramatically improved her quality of life during wakefulness. This report may be a clue to discuss the function of sleep-onset REM sleep seen in the early stage of life and suggests that nasal mask ventilation is a viable option in selected cases with congenital central hypoventilation syndrome (CCHS).