A retrospective study was carried out to determine the frequency of early periodontal bone loss in 15 year olds as seen in bite-wing radiographs. A total of 468 radiographs of 15 year olds was examined, 246 from 1970-74 and 222 from 1978-80. The alveolar bone crest on the mesial and distal of the first permanent molar teeth was examined for radiographic evidence of early chronic periodontitis. The condition of the adjacent proximal tooth surfaces was also recorded. No significant difference was found between the two groups; 39% of the 1978-80 and 43% of the 1970-74 group showed radiographic evidence of early chronic periodontitis (P less than 0.05). Males and females showed a similar frequency of periodontal disease levels. The mesial interproximal space of the first molars had significantly higher frequencies of radiographic evidence of chronic periodontitis than the distal interproximal spaces in the two groups examined. Fewer proximal restorations with overhangs were noted in the 1978-80 group, however more proximal subgingival calculus was found in this group than the 1970-74 group.