This study was undertaken to determine the optimal concentration of a povidone-iodine solution (Neojodin: NJD) for irrigation of subgingival pockets. Three different dilutions were prepared (undiluted, 20%, and 10%). Statistically significant reduction of total colony forming units (CFU) was shown after irrigation with undiluted NJD solution when compared to control sites. Although reduction was not significant after irrigation with 20% or 10% NJD solution, total CFU were reduced to less than 1% in several sites, which was not true with biological saline.