Oral Microbiology is an important emerging field of study. This article is from the Journal of Oral Microbiology (www.JournalofOralMicrobiology.net). All users are granted free access to the article under a Creative Commons License. In this article Lakio et al. investiate the possibility of using plasma antibody measurements of antibody levels to periodontal pathogens as support for identifying diagnosis, disease activity, classification, and prognosis of periodontitis. The aim of this study was to investigate the long-term stability of plasma antibody levels against Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis. The study concludes that Plasma IgG levels against A. actinomycetemcomitans and P. gingivalis are extremely stable during 15 years both in subjects with and without periodontitis.