This study was to determine the markers representative of pathogenic periodontal microflora [Prevotella intermedia (P.i), Tannerella forsythia (T.f) [Bacteroides forsythus], Treponema denticola (T.d), Actinobacillus actinomycetemcomitans (A.a), Porphyromonas gingivalis (P.g)] in the dental plaque of adolescents with various degrees of severity of periodontium inflammation. Forty-patients aged 15-16 years of age were examined using PMA, CPI and Green-Vermillion indices (Müller 2001). The hygiene status of each patient was also determined using Durr Dental's Vista Proof intraoral camera (Germany). The polymerase chain reaction (PCR) was performed using a Biometra Thermocycler to detect DNA of pathogenic periodontal bacteria in dental plaque. All marker microorganisms (P.i.+T.f.+T.d.+A.a.+P.g.) were identified in patients diagnosed with periodontitis in dental plaque. A direct correlation between the level of oral hygiene and the severity of the pathological process in it was determined. It was found that the increase in the severity of the disease was accompanied by increased pathogenic periodontal microflora in dental plaque. Identification of periodontal pathogens in dental plaque by PCR greatly enhances the early diagnosis of Cronic cattaral gingivitis (CCG) risk factors in adolescents, and allows for detailed analysis of the relation between each factor and severity of the process. This method may be used for the diagnosis of periodontal diseases, prediction of their future course, and reasonable choice of antimicrobial therapy.