Background:The investigation of subgingival microflora in type 2 diabetic patients with periodontitis presented conflicting results. Aim: To determine the presence of Porphyromonas gingivalis, Tannerella forshytia, Treponema denticola and Aggregatibacter actinomycetemcomitans in subgingival biofilm of patients with diabetes type 2 and to relate it to the degree of metabolic control. Method: A descriptive study, which analyzed 23 diabetic patients consecutively referred from the Internal Medicine Unit of Medicine Faculty at Universidad de los Andes was conducted. After obtaining an informed consent from the patients a clinical examination that included measurements of periodontal pocket depth, clinical attachment level and gingival bleeding was performed. The patients were classified according to the severity of periodontitis and metabolic control of diabetes as determined by an average of 3 of glycosylated haemoglobin tests. Microbial technique was performed by chain reaction of polymerase. Results: In the group of patients examined the most prevalent bacteria were, Treponema denticola and Tannerella forsythia (65.2%), followed by Porphyromonas gingivalis (17.3%) and Aggregatibacter actinomycetemcomitans (13%). Patients with poor glycemic control had a greater presence of Treponema denticola, Tannerella forsythia, Porphyromonas gingivalis and Agreggatibacter actinomycetemcomitans and an increase in the rate of bleeding on probing. Conclusions: In the group of diabetic patients studied, the most prevalent bacteria were Treponema denticola and Tannerella forsythia. Type 2 diabetic patients with moderate and poor glycemic control had a higher presence of these microorganisms, compared to groups with higher levels of glycemic control.