The present study was designed to investigate the effect of scaling and root planning (SRP) on the expression of TNF-α in gingival crevicular fl uid of patients with aggressive periodontitis (AgP) and chronic periodontitis (CP) compared to controls. Methods: 45 patients were selected and grouped into 3 groups, the fi rst group included 20 patients with AgP, the second group included 20 patients with CP, and third group with 5 periodontally healthy subjects (C). They were treated with SRP plus antibiotics. Periodontal clinical parameters were recorded before and after treatment as well as gingival crevicular fl uid (GCF) levels of TNF-α from all subjects were estimated before and after treatment using enzyme linked immunosorbant assay (ELISA). Results: levels of TNF-α in clinically healthy subjects were statistically signifi cant lower than those in diseased sites of CP and AgP. Also, SRP resulted in a statistically decreased expression on TNF-αlevels from diseased sites of both CP and AgP. All clinical parameters were statistically different between CP and AgP and before and after SRP (P ≤ 0.05). Conclusion: TNF-α could be considered as an important biomarker in determining disease activity and response to treatment