Background: Cathelicidin LL-37, an antimicrobial peptide, is part of the host innate immune response in the oral cavity. This study was aimed at analyzing the effect of scaling and root planing on LL-37 levels in gingival crevicular fluid (GCF) of chronic periodontitis patients. METHODS: Systemically healthy 10 control subjects (group 1) and 20 chronic periodontits (group II) were included in this study. Plaque index, gingival index, probing depth and clinical attachment levels were recorded and GCF samples were collected in group 1 from one site at the initial visit only. 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 another one with healthy periodontium.GCF samples were quantified for LL-37 levels using ELISA. RESULTS: In the present study, significant reductions in clinical index scores were noted in group II after treatment. Before treatment, diseased site of group II showed the highest LL-37 level, non periodontitis site of group II showed lower LL-37 level, group 1 showed the lowest LL-37 level. After treatment, treated sites of group II showed the highest LL-37 level, non periodontitis site of group II showed lower LL-37 level, control group showed the lowest LL-37 level. CONCLUSIONS: This study showed that scaling and root planing was effective in reducing GCF levels of LL-37 from inflamed periodontal sites. Hence LL-37 can be considered as an "inflammatory marker" can be explored in future as a potential therapeutic target in the treatment of periodontal disease.