Dental caries is the most infectious and communicable dental disease of all age groups, which effects overall health of an individual. Childhood caries is a multifactorial dental disease and if left untreated it leads to discomfort, pain and lack of interest in routine activities and ultimately destroys tooth structure and early loss of tooth. Steptococcus mutans (S.mutans) is the main cariogenic microorganism. S.mutans breaks down sugar for energy and produces acidic environment, which causes demineralization of superficial structures of tooth i.e. enamel and dentin resulting in dental caries. It can be transmitted horizontally and vertically. According to the recent studies vertical mode of transmission is more common in preschool children than horizontal. Mainly the transferred genotypes are responsible for the transmission of caries from mothers to their children. There is genotypic diversity in population to population. No such relevant study has been conducted on local population so there is a need to know the main cariogenic genotypes of S.mutans and its transmission from mothers to their children in local population.