Aim: Evaluation of biological and clinical effects of Antibody against periodontal pathogenic bacteria. This study analysis  immunoglobulin  serum IgG  to A.A and P.G in chronic and aggressive periodontitis patients  . Subjects and methods: Thirty participants were involved in this study. Ten patients with chronic , Ten patients with aggressive as study groups and other ten healthy  subjects were chosen for the study as a control group. Clinical periodontal parameters (Periodontal pocket depth, Clinical attachment loss and Bleeding on probing) were recorded at baseline for three groups (study and control group) and after treatment which is scaling and root planning accompanied by antibiotic for the study groups.  Serum samples were be taken two times (at baseline and four weeks after treatment) from each patient in the study group. The patient will be treated twice a week for three weeks. However in control group serum sample was taken only once. The blood samples will be analyzed using ELISA Assay Kit. Results: Serum IgG level showed  a significant difference higher in chronic and aggressive periodontal patients (study groups) compared to healthy subjects  (control group) at baseline (p < 0.05).  Concerning the study groups, four  weeks after treatment, the mean values of serum IgG level was not significantly reduced compared to its value at baseline (P > 0.05 ).Moreover, there was no statistically significant differences between two study group after treatment a(t P > 0.05) . Conclusion: Serum levels of IgG antibodies againstA.actinmycetemcomitans  orP.gingivalis in chronic and aggressive periodontitis patients  suggested to play a protectivre role against periodontal infections with these microorganisms . Serum IgG level have a positive correlation with pathogenic bacteria of  periodontitis. Serum IgG level might be a suitable marker for monitoring treatment in  periodontal disease . Key word  immunoglobulinIgG ,  periodontitis