The long term success of periodontal treatment is dependent upon the effectiveness of the main-tenance care program after active treatment. The purpose of this study was to evaluate whether nutraceutical containing PRF-K2 as natural product from plant and seaweed has beneficial effects on clinical parameters, gingival crevicular fluid (GCF) volume and GCF cytokine levels during main- tenance phase after periodontal treatment. Among the generally healthy and non-smoking. moderate to severe chronic periodontitis patients during maintenance phase in Department of Periodontics, Chonnam National University Hospital, twenty eight patients took nutraceutical containing PRF-K2 (Oscotec Inc. Cheonan, Korea) for 3 months as experimental group and sixteen patients received only maintenance care as control group. Clinical examination and GCF collection were performed at baseline, 1, 2 and 3 months of experiment. Total amounts and concentrations of GCF IL-1{eta}, IL-1ra and $PGE_2$ were evaluated using ELISA kit. In probing pocket depth, experimental group showed the tendency of more reduction than control group after 3 months of experiment. Sulcus bleeding index (SBI) and GCF volume were significantly decreased in experimental group(p<0.05), whereas they were increased in control group. GCF IL-1{eta} level tended to decrease in both experimental and control group and IL-1ra concentration tended to increase in experimental group and to decrease in control group. IL-1ra/IL-1{eta} ratio tended to increase in experimental group and to decrease in control group during experimental period. GCF $PGE_2$ amount did not show any change in experimental group and tended to increase in control group. These results suggest that nutraceutical supplement which contain PRF-K2 could improve perio-dontal condition during maintenance phase after periodontal therapy.