The oral cavity is inhibited by many of the bacterial species. Some of them have a key role in the development of oral disease. Interrelationships between oral microbiome and systemic conditions such as head-and-neck cancer have become increasingly appreciated in recent years. Emerging evidence also suggests a link between periodontal disease and oral cancer, and the explanation being that chronic inflammation could be a major factor in both diseases. Squamous cell carcinoma is that the most frequently occurring malignancy of the oral cavity and adjacent sites, representing over 90% of all cancers. The incidence of oral cancer is increasing, significantly among young people and women. Worldwide there are 350,000–400,000 new cases diagnosed every year. Bacteria, viruses, and fungi are strongly implicated as etiological factors in certain cancers. In this review we will discuss the association between the development of oral cancer in potentially malignant oral lesions with chronic periodontitis, chronic Porphyromonas gingivalis, Fusobacterium nucleatum, candida, other microbes and described mechanisms which may be involved in these carcinoma.