Recent research evidence shows that the receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG) play an important role in osteoclastogenesis and the inflammatory bone loss during periodontitis. Bone remodeling process is dependent on the balance of these two proteins while a high ratio of RANKL/OPG characterizes the increased osteolytic process and it has been reported in inflammatory diseases including the periodontal disease. The purpose of this study was to determine the OPG and RANKL mRNA levels in periodontal tissues derived from patients with advanced chronic periodontitis after non-surgical periodontal therapy (SRP) and to compare the RANKL/OPG ration with that in healthy persons. Gingival biopsies were obtained from subjects with clinically healthy periodontium (H) (N = 11) and patients with advanced chronic periodontitis (CP) (N = 14). Total RNA was isolated from the gingival samples and 1 microg RNA was reverse transcribed to cDNA, followed by polymerase chain reaction (PCR) using specific primers for OPG and RANKL. The efficiency of reverse transcription was verified by the amplification of the GAPDH gene. The intensity of RT-PCR products was analyzed by a densitometer and was normalized to the intensity of the band for the housekeeping gene GAPDH. Immunohistochemical evaluation of the RANKL and OPG expression was also performed. The expression of RANKL as well as of OPG was reduced in CP specimens in comparison to that of healthy persons in a statistical significant way. However, the RANKL/OPG ratio showed to be slightly elevated in CP compared to H specimens but this finding was not of statistical significance. The immunohistochemical analysis revealed a non-uniform expression pattern for both proteins. Although further investigation is needed to identify the specific role of RANKL and OPG protein in periodontitis progression, our data after SRP might indicate the possible involvement of these proteins in the activation of pathways, which regulate the repair of the periodontal tissues.