Dental Caries is a common, chronic disease of childhood. Most studies that have assessed risk factors for dental caries focused on non-modifiable risk factors such as previous caries experience and socioeconomic status. It is also important to investigate modifiable risk factors that can be used in developing guidelines for risk assessment and prevention. This review discusses about dental caries in childhood and it__ampersandsignlsquo;s association with Streptococcus mutans, discusses the colonization of Streptoccus mutans, Origin of Streptococcus mutans, factors affecting colonisation of oral cavity in children, and prevention of transmission of Streptoccus mutans from mother to child in detail.