The aim of the present study was to assess the incidence of early radiographic bone loss in a birth cohort over 8 years and to assess possible associations between incidence of bone loss and reported dental behavior, ethnic background, and previous orthodontic treatment. In a case control study comprising a proportion of the study population, the detection of black pigmented Bacteroides and Actinobacillus actinomycetemcomitans and their association with early radiographic bone loss was assessed. At the beginning of the study in 1984, there were 2,767 subjects. In 1992 sets of bite-wing radiographs were obtained from 215 subjects, who also filled out a questionnaire concerning their present and past dental behavior, ethnic background, and orthodontic treatment. Radiographic alveolar bone loss was recorded if the distance from the cemento-enamel junction to the alveolar crest exceeded 2 mm. Thirteen subjects (6%) showed new sites with bone loss over the 8-year period. Subgingival plaque was sampled from these 13 subjects and from 13 control subjects. None of the independent variables could be associated with the observed incidence of radiographic bone loss in this cohort, with the possible exception of the presence of A. actinomycetemcomitans which was detected in about 50% of the new sites with bone loss.