Statement of Problem: One of the best ways for treatment of Aggressive Periodontitis (AP) is identification and elimination of etiologic factors specially two microorganisms Actinobacillus actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) in patients harboring them.

Purpose: This study determines the prevalence of Aa and Pg and its correlation with age, sex and the number of family members as well as probing pocket depth (PPD) in active sites of AP patients, referred to department of periodontics, Faculty of Dentistry, Tehran University of Medical Sciences.

Materials and Methods: In this cross sectional, descriptive study, 54 sites (PPD> 5mm) in 15 patients were considered for culture. Marginal gingiva was dried and sampling performed by paperpoint (#30). The selective medium for Aa, was Trypticase Soy Agar-Bacitracin- Vancomycin (TSBV) and for Pg was Brucella agar.Results were analyzed using Fisher and Chi-Square statistical tests.

Results: Thirteen patients or 38 sites (70.4%) were identified as Aa positive and 3 patients or 10 sites (18.4%) were Pg positive. There was no significant relation between the presence of Aa and sex or age (P=0.086). Pg was more prevalent in men compared with women (P<0.0001) but with regard to age there was no statistical difference between men and women. Aa had a significant positive correlation with PPD (P=0.002), which was not true for Pg. In addition, the number of positive sites showed a significant negative correlation with the number of family members.

Conclusion: Based on the present study, the prevalence of Aa in deep pockets in patients with AP is higher than Pg.