A longitudinal study of 127 children between the ages of 11 and 17 years revealed a high initial prevalence of gingivitis that tended to decline slightly with age. The distribution of the ages of the children when experiencing their observed maximum amount of gingivitis was consistent with the hypothesis that there is a relationship between puberty and gingivitis. There was also evidence that at the time of the peak gingivitis experience the gingival tissues were exhibiting a heightened response to irritation.