Porphyromonas gingivalis, a black-pigmented gram-negative anaerobic rod, has been implicated as a major pathogen of chronic periodontitis .It possesses all characteristics that make it an important member of periodontopathic microbiota - it is essentially absent in oral health & is a predominant member of the subgingival microbiota in disease and possesses and "excretes" numerous potentially toxic virulence factors. P gingivalis also produces many cell components and macromolecules that have been proposed to function as virulence factors. P.gingivalis produces a large number of hydrolytic, lipolytic and proteolytic enzymes. Major emphasis during the past several years has concentrated on the isolation and characterization of protein . Now several vaccines have also been formed to prevent against oral infections.