The objective of this review is to bring the reader up-to-date on the current understanding of chronic and aggressive forms of periodontitis and the implications for diagnosis and treatment of these diseases. The only difference between chronic periodontitis and aggressive periodontitis with regard to tissue destruction appear to be perhaps the magnitude, sequelae, and control of the response. While there may be some differences in the cellular infiltrate between these two diseases, the molecular mediators and pathologic processes are generally the same.