 This study was designed to determine whether a simple manipulative technique of relaxing the tissues of the occipito-atlantal junction in the neck had any effect on the activity of the sympathetic or parasympathetic nervous system. Subjects were dark adapted then measures of pupillary activity, reflecting autonomic nervous system activity were taken before and after treatment. The study hypothesis was that thet treatment technique would have no effect on the pupillary measures, hence indicating no effect on autonomic system activity. 