Four hundred and ninety three ninth and tenth graders participated in a study in York County, Virginia designed to compare the effectiveness of traditional plaque control methods with self-assessment of gingival bleeding as approaches to the prevention of gingivitis in teenagers. At baseline examination in April 1987 participants were examined for periodontal health, DMFS, and gingival recession. Questionnaires regarding oral hygiene methods and professional care practices were completed. Subjects were then randomly assigned by grade to a positive control plaque group or to a test self-assessment of bleeding group. Dental hygienists provided appropriate instruction using manuals outlining procedures for the identification of plaque or the self assessment of gingival bleeding. Two weeks following this classroom based instruction, individual instruction was held to reinforce each message. One year later each participant had individual instruction with the dental hygienist and the opportunity to have an oral prophylaxis. Four interim examinations to assess periodontal health were conducted. The final examination, in April 1989, assessed DMFS, gingival recession and periodontal status. A dramatic decrease in the mean number of bleeding sites in both the plaque control and self assessment of gingival bleeding groups was found for the 356 remaining subjects. Data analyses are completed and manuscripts are in review.