The aim of the present study was to evaluate the mean bacterial load of some periodontal pathogenic bacteria in Italian patients affected by chronic periodontitis. The sample consisted of 1,762 patients with a clinical diagnosis of chronic periodontitis based on the criteria of the American Academy of Periodontology sampled in the period 2013-2015; 1,323 patients were from Northern Italy, 317 from Central Italy and 122 from Southern Italy. Samples for microbiological analysis were collected from the four sites of the greatest probing depth in each patient and then processed by quantitative polymerase chain reaction. Periodontal pathogens have the following percentage respect to total bacteria load: Aggregatibacter actinomycetemcomitans 0.1%, Campylobacter rectus 2%, Fusobacterium nucleatum 8%, Porphyromonas gingivalis 6%, Treponema denticola 2% and Tannerella forsythia 1.5%. There are significant differences in bacterial load among the different geographical areas both for the total bacterial and for the single species. The results of our study in this Italian population showed that a different geographic distribution exists among periodontal pathogens. We hypothesize that these differences in bacterial load could be related to genetic and environmental factors. Additional studies are necessary to confirm these data and to get more insight on additional factors, which may play a role in periodontal pathogens in different geographic areas.