A review of the literature on juvenile periodontitis has been undertaken. This paper traces the historical development of the appreciation of the condition. Some of the numerous early attempts to define a systemic background are noted, and the concept of 'periodontosis' and its subsequent influence, e.g. on epidemiological and clinical studies are discussed. The refining over the last 20 years of the concept of aggressive periodontal disease in the young is recorded. The patterns of bone loss in juvenile periodontitis and some forms of treatment are presented, together with evidence on its histopathology. Recent research has tended to concentrate on the microbiology and immunological background of juvenile periodontitis and a number of these studies are discussed.