Inflammatory cytokines may have important roles in periodontitis. We assessed the effects of initial periodontal therapy on clinical periodontal parameters and interleukin-1β (IL-1β) level in gingival crevicular fluid (GCF) from chronic periodontitis (CP) patients. After initial screening, baseline periodontal parameters such as probing pocket depth (PPD) and bleeding on probing (BOP) were measured. GCF samples were collected from 13 shallow (≤3 mm) and deep (≥5 mm) PPD sites from 13 CP patients, and GCF volume and IL-1β concentration were determined at baseline (before scaling and root planning) and at 2 and 4 months after initial therapy. Baseline BOP rate, GCF volume, and IL-1β level were significantly higher at deep PPD sites than at shallow PPD sites. Significant improvements in PPD and BOP were observed at 2 and 4 months after periodontal initial therapy in deep PPD sites only. In contrast, GCF volume and IL-1β concentration were lower at 2 and 4 months after initial therapy at all sites. These results suggest that GCF volume and IL-1β level in samples reflect disease severity and that these variables are better than PPD and BOP as markers of gingival inflammation. (J Oral Sci 57, 67-71, 2015)