Medically healthy subjects (N = 103), 10-32 years of age, with localized (juvenile periodontitis = JP) or generalized (severe periodontitis = SP) advanced periodontal disease were analyzed for interrelationships of sex, race, age and clinical findings. Females predominated (2:1) in both JP and SP. There were significantly more subjects of the black race in JP, but when age was included as a cofactor the race distinction became insignificant. While whole mouth Plaque and Gingival Indices were lower in JP, these values at sites with attachment loss were equally high in both groups. Extent of disease was significantly related to both plaque and age in SP, and to plaque but not to age in JP. This suggests the existence of a factor(s) in JP which interfere(s) with the age-plaque-disease relationships found in SP and present in adult periodontitis. Contrary to implications of some definitions of JP, periodontal attachment loss was strongly associated with plaque and gingival inflammation in both localized and generalized patterns of disease.