DESIGN: Sixty five subjects presenting at least twelve teeth with probing depth (PD) ≥4 mm were selected. 33 subjects were randomly assigned to full-mouth SRP + Septilin (group 1) and 32 subjects were assigned to full-mouth SRP + Placebo (group 2). The clinical outcomes evaluated were plaque index (PI), gingival index (GI), clinical attachment level (CAL), PD and % of sites with bleeding on probing (%BOP) at baseline (B\L), 10 days, 1, 3 and 6 months interval and percentage of sites positive for A. actinomycetemcomitans, P. gingivalis and T. forsythia were recorded at B/L, 3 and 6 months using polymerase chain reaction.