Objective: The aim of the study was to assess the level of total oxidant capacity (TOC) in gingival crevicular fluid (GCF) of patients with moderate chronic periodontitis before and after non-surgical periodontal treatment.Material and methods: The study included 30 patients, divided into 2 groups :Group I (Control group):Consisted of 10 healthy individuals and Group II (Study group): Consisted of 20 patients with moderate chronic periodontitis. The level of TOC was measured before treatment and 4 weeks after in non surgical periodontal therapy. In group I, GCF samples were collected from one site at the initial visit only and in group II, GCF samples were collected at the initial visit and 4 weeks after treatment from two sites: The most periodontally affected site and a healthy site.Results:As regards TOC, before treatment, diseased sites of periodontitis group showed the statistically significantly highest mean TOC level, followed by healthy sites of periodontitis group followed by control group.