Aim The aim of this study was to measure the level of Oncostatin M (OSM) a gp130 cytokine in the gingival crevicular fluid (GCF) and serum of chronic periodontitis patients and to find any correlation between them before and after periodontal therapy (scaling and root planing,SRP). Methodology 60 subjects (age 25-50 years) were enrolled into three groups (n=20 per group),group Ⅰ (healthy),group Ⅱ (gingivitis) and group III (chronic periodontitis). Group Ⅲ subjects were followed for 6-8 weeks after the initial periodontal therapy (SRP) as the group Ⅳ (after periodontal therapy). Clinical parameters were assessed as gingival index (GI),probing depth (PD),clinical attachment level (CAL),and radiographic evidence of bone loss. GCF and serum levels of OSM were measured by using Enzyme Linked Immunosorbent Assay (ELISA). Results It was found that mean OSM levels had been elevated in both the GCF and serum of chronic periodontitis subjects (726.65 ± 283.56 and 65.59 ± 12.37 pg·mL-1,res-pectively) and these levels were decreased proportionally after the periodontal therapy (95.50 ± 38.85 and 39.98 ± 16.69 pg·mL-1 respectively). However,OSM was detected in GCF of healthy subjects (66.15 ± 28.10 pg·mL-1) and gingivitis-suffering subjects (128.33 ± 22.96 pg·mL-1) and was found as below the detectable limit (≈0.0 pg·mL-1) in the serum of same subjects. Significant correlation has been found between clinical parameters and GCF-serum levels of OSM. Conclusion Increased OSM level both in the GCF and serum,and the decreased levels after initial periodontal therapy (SRP) may suggest a use as an inflammatory bio-marker in the periodontal disease. Aim The aim of this study was to measure the level of Oncostatin M (OSM) a gp130 cytokine in the gingival crevicular fluid (GCF) and serum of chronic periodontal patients and to find any correlation between them before and after periodontal therapy (scaling and root (n = 20 per group), group I (healthy), group Ⅱ (gingivitis) and group III (chronic periodontitis). Group Ⅲ subjects (age 25-50 years) were enrolled into three groups were followed for 6-8 weeks after the initial periodontal therapy (SRP) as the group Ⅳ (after periodontal therapy). Clinical parameters were assessed as gingival index (GI), probing depth (PD), clinical attachment level Radiographic evidence of bone loss. GCF and serum levels of OSM were measured by using Enzyme Linked Immunosorbent Assay (ELISA). Results It was found that mean OSM levels had been elevated in both the GCF and serum of chronic period subjects (726.65 ± 283.56 and 65.59 ± 12.37 pg · mL-1 , res-pectively) and these levels were proportionally after the periodontal therapy (95.50 ± 38.85 and 39.98 ± 16.69 pg · mL-1 respectively). However, OSM was detected in GCF of healthy subjects (66.15 ± 28.10 pg · mL- ) and gingivitis-suffering subjects (128.33 ± 22.96 pg · mL-1) and was found as below the detectable limit (≈0.0 pg · mL-1) in the serum of the subjects. Significant correlation has been found between clinical parameters and GCF -serum levels of OSM. Conclusion Increased OSM level both in the GCF and serum, and the decreased levels after initial periodontal therapy (SRP) may suggest a use as an inflammatory bio-marker in the periodontal disease.