Objective: The effect of vit (C) as antioxidant on the level of Total Oxidant Capacity (TOS) in Gingival Cravicular Fluid (GCF) of smoker patient with Chronic Periodontitis (CP) after phase 1 therapy.Patients and Methods: The study included 40 patients, all are systemically healthy and heavy smokers. All patients had moderate to advanced generalized chronic periodontitis with a minimum of 2 sites of clinical attachment loss (CAL) more than 4 mm with radiographic evidence of bone loss. The study groups were divided in to 2 groups : Group 1 : consisted of 20 patients who were treated with scaling and root planning .Group 2 : Consisted of 20 patients who were treated with scaling and root planning in conjunction with 2g antioxidant Vit (C).Clinical measurements including Gingival index (GI), Plaque index (PI), bleeding on probing (POB), Probing depth (PD), Clinical attachment loss (CAL) . GCF samples were collected at the initial visit and collected again 4 weeks after treatment.Results: there was a highly statistically significant reduction in mean values of TOC in antioxidant group (A group) while no significant change in mean values of TOC was noted in non antioxidant group (NA group).Conclusion: From the present study the following can be concluded: 1- In smokers with chronic periodontitis, phase I periodontal therapy alone was unable to restore the oxidant – antioxidant imbalance. 2- The adjunctive use of vitamin C for management of chronic periodontitis in smokers showed predictable clinical and biochemical outcomes.