Objective To determine whether there is some relationship between sulcular sulfide level and severity of periodontitis.Methods Fifteen systemically healthy subjects diagnosed with aggressive periodontitis(AgP) and sixteen systemically healthy subjects diagnosed with chronic periodontitis(CP) were included in this study.Clinical periodontal parameters such as plaque index,probing depth,attachment loss,bleeding on probing(BOP) et al,were recorded.The volatile sulphur compounds (VSC) level in periodontal pockets was measured using a portable monitor in a digital score ranging from 0.0 to 5.0 in increments of 0.5.All of 5220 sites for 870 teeth were included in this study.Results For both AgP and CP subjects,the clinical periodontal parameters were found significantly higher in VSC-positive sites than in VSC-negative sites(P0.001).The VSC level has significantly positively correlated with clinical periodontal parameters(P0.001).The VSC level and percentage of VSC-positive sites were found significantly higher in moderate-to-deep pocket sites than in shallow pocket sites(P0.001).The VSC level and percentage of VSC-positive sites were higher in sites with attachment loss than those in sites without attachment loss in the same probing depth group.Conclusion The VSC level may be a potential indicator for detecting severity of both AgP and CP.