In general, the new term "localized aggressive periodontitis" replaces what was previously known as "localized juvenile periodontitis." Similarly, "generalized aggressive periodontitis" replaces what used to be called "generalized juvenile periodontitis." Aggressive periodontitis is a specific type of periodontitis with clearly identifiable clinical and laboratory findings, making it sufficiently different from chronic periodontitis and warranting separate classification. Not all the characteristics must be present to assign a diagnosis or classify the disease. The diagnosis may be based on clinical, radiographic, and historical data, and laboratory testing may not be essential for assigning a diagnosis.