Background The role of microorganisms in the etiology of periodontal disease is well understood. The association of specific organisms in the pathogenesis of periodontal disease was established by the specific plaque hypothesis. This study examined the effects of periodontal surgery on Aggregatibacteractinomycetemcomitans (Aa) levels in localized aggressive periodontitis before and after periodontal surgery. Method: A clinical study was done on 24 male and 16 female patients who underwent surgical periodontal therapy. Bacterial counts were assessed from the plaque samples and gingival specimens. Results: Mean reduction of pre and post operative bacterial counts were statistically significant at 1%.COnclusion: A reduction of bacterial count was observed in plaque and gingival tissue samples after surgery.