Aim: To know the role of these microorganisms as etiological agents in chronic periodontitis and their role in the severity of the disease. Material and Method: A total of 300 patients with chronic periodontitis and 300 age and sex matched controls were enrolled with prior informed consent. Sub gingival plaque specimens was collected and processed for bacterial and yeast etiology. The data was analyzed by using SPSS software and Chi square test with p-value of __ampersandsignlt;0.0001 was applied. Results: The most common age group affected were 31 to 40 years and male were outnumbered the female patients but the difference was not statistically significant. Overall detection rate of aerobes, anaerobes and yeasts were 47.3%, 78.3% and 4.6% respectively. The most common etiological agents significantly associated belong to anaerobes and yeasts. Anaerobes were found to be associated significantlywith severity of disease. Conclusion: Peptostreptococcus anaerobius, Veillonella parvula and Porphyromonas gingivaliswere predominant etiological agents implicated as etiological agents in chronic periodontitis. Aerobes were significantly associated with mild chronic periodontitis while anaerobes found to be significantly associated with severe chronic periodontitis.