Abstract
This study was presented in order to compare two mass outbreaks of hyperventilation syndrome among high school girls in Nagoya and its neighborhood.One outbreak, named acute type, was observed during the training in a volleyball club of a private girl's high school. Hyperventilation attacks spreed out to 5 girls on the first day and 2 girls on the following day. The common physical and psychological backgrounds, such as fatigue, tension against the tournament, physiological hyperventilation etc, did play an important role in this group.The other epidemic, named chronic type, happened in a coeducational junior high school near Nagoya. Eight pupils in all, who were either classmates or clubmates, were involved in the mass outbreaks of almost 10 months long. Although definite and common back grounds, were not found, like in the acute type, the results of the analysis of YG test, egogram and environment showed the inclination mass outbreaks of hyperventilation. Hyperventilation attacks of this type seemed to be a manifestatin of regressive mechanism to intend to mantain the position of the star or to desire to impress their existence. It seemed to be more difficult to control the latter type at school because of their complicated mechanism.