The prevalance and severity of caries in children under three years old are constantly increasing. One of the cause is the increase consumption of cariogenic carbohydrate. Breast milk have buffer capacity eventually able to prevent caries. The aim of this research are to discover the correlatoin between breastfeeding with the saverity of Early Childhood Caries (ECC) in children under three year old to provide information on prevelance and severity of caries in children under three years and to explain factor influancing the incidance of ECC. The research designed cross sectionally and conducted upon 565 children aged 12-38 months selectes using multistage cluster random sampling. the ECC prevalence of children under three years in DKI Jakarta is 52.7% with average scor of def-t2.85. Bivariate analysis showed that variable which corralate with the level of ECC are the way to deliver (p 0 012) frequency (p 0 002) duration (p 0 002) salivary buffer capacity (P 0 013) habitual consumption of sugary died (p 0 005) child s dental hygiene behavior (p 0 002) and mother s education (p 0 001). Multivariete analysis showed that ECC can be explained by these variables age mother s education the way to deliver and frequency of breast milk complements/replecement of consumtions chid s brushing habit plaque pH and salivery buffer capacity. resulting determination of coefficient 32.1%. There is no significant correlation between breastfeending and the level of Early Chilhood Caries (ECC). The role of protective qualities of bteastfeending are not shown because of bias in obtaining data influence the incidence of caries.