ECC was defined by the American Academy of pediatric dentistry at 2003 as the presence of 1 or more decayed (noncavitated or cavitated lesions), missing (due to caries), or filled tooth surfaces in any primary tooth in a child 71 months of age or younger. This is a virulent type of dental caries that start soon after the tooth erupts and progress rapidly. The prevalence is 1-12% in developed countries and 70% in developing countries, and changes in different cultures, communities, socioeconomic status, etc. The etiology of the disease is multifactorial like in any dental caries. The risk factors include high levels of SM and LB, enamel defects, oral habits, complication at pregnancy and birth, social and demographic factors and the child's age. The disease implications are: high risk of new caries defects in both permanent and deciduous dentitions, insufficient physical development, hospitalization and emergency room visits, loss of school days and increased days with restricted activity, increased treatment costs and time, diminished ability to learn, and diminished oral health-related quality of life. Due to the aggressive pattern of the disease, treatment should be specific for each individual patient, and should be given by an expert dentist with experience who could manage the young child and the process of the disease. Treatment options are: 1. Conservative approach which includes recalls and topical fluoride, 2. Aggressive restorative approach. In both we should first stop the carious habit and encourage prevention. Before choosing the type of treatment, we should consider the severity of the lesions, child's age, caries risk, child's behavior, and parents' cooperation. Prevention at home includes: 1. decreasing the mother's/primary caregiver's mutans streptococci levels, 2. avoid sharing the same utensils in the family, 3. implementing oral hygiene measures as the first primary tooth erupts, 4. dental home, 5. avoid inappropriate feeding practices of infants and toddlers. Prevention at clinic includes: 1. topical fluoride application, 2. proximal slices in appropriate cases.