There are conflicting data regarding the role of interleukin (IL)-17 in periodontal health and disease. However, IL-18 levels are known to increase with the severity of periodontal disease. The present study was performed to explore the role of these proinflammatory cytokines in periodontal disease progression, and also to clarify the effect of periodontal treatment on their concentration. Sixty age- and gender-matched subjects were divided into three groups each consisting of 20 subjects on the basis of gingival index (GI), probing pocket depth (PPD), clinical attachment loss (CAL) and radiological parameters (bone loss): healthy (group 1), gingivitis (group 2) and chronic periodontitis (group 3), while group 3 patients after treatment constituted group 4. GCF samples collected from all the groups were assayed by enzyme-linked immunosorbent assay to estimate the levels of IL-17 and IL-18. IL-18 levels in GCF increased proportionally with the severity of periodontal disease, and decreased after treatment. However, IL-17 levels in GCF were nearly zero. Since our data indicate an absence of IL-17 in GCF, it cannot be considered as a biomarker of periodontal disease progression, at least in Indian populations. However, IL-18 appears to be a good inflammatory biomarker.