Night terrors are a sleep disorder, resulting from a partial arousal during slow-wave sleep. They usually occur within 2 hours of sleep onset and are characterized by agitation and unresponsiveness to external stimuli. Nineteen children (ten males, nine females) with onset of night terrors before age 7.5 years were studied by means of a questionnaire. Mean observation time (time from onset age to age at survey) was 8.5 years, but longer than 10 years in nine subjects. Seventy percent of the children had their initial frequency of night terrors as their peak frequency, with a tendency for shorter duration of the parasomnia in this group. Children with onset age less than 3.5 years may be expected to attain a peak frequency of at least one episode per week. Children with onset after 3.5 years, but before 7.5 years, may expect to attain a peak frequency of 1-2 episodes per month. There was a mean duration of 3.9 years, with a tendency for longer duration in children with positive family histories of sleep walking. Fifty percent stopped by age 8 years; 36 percent continued into adolescence. No common abnormal behavioral profile or psychopathology was found. Common precipitants of attacks were not identified.