Background: Oral cavity reflects the general health status of an individual and is colonized by more than seven hundred species living in its own domain and balances the normal oral ecology. This ecosystem tends to get altered when there is a local or systemic disease. One among the systemic diseases, Diabetes Mellitus a common life style disease has an influence on the microbiota which in turn tends to shift the ecosystem. Thus the aim & objective of the study is to identify the Carriage rate of Streptococcus mutans from five anatomical surfaces of oral cavity of Type I and Type II Diabetes Mellitus and Non Diabetic population & to compare carriage rate Streptococcus mutans of Type I and Type II Diabetic patient with Non Diabetic population. Materials and Methods: Swabs were collected from five different anatomical sites of the oral cavity from Type I & Type II and Non Diabetic patients of 30 each. Samples were confirmed for the species and then inoculated in Mitis Salivaris Agar to assess the Frequency of isolation and Colony Forming Units (CFU) of Streptococcus mutans. Results: Observation of the study revealed that the Frequency of Isolation and Colony Forming Units were high in patients with Type II Diabetes Mellitus when compared to that of Type I Diabetes Mellitus and the Non Diabetes Mellitus subjects.