The 2000 Surgeon General’s Report on Oral Health included a limited discussion of the condition known as early childhood caries. Because of its high prevalence, its impact on young children’s quality of life and potential for increasing their risk of caries in the permanent dentition, early childhood caries is arguably one of the most serious and costly health conditions among young children. A necessary first step in preventing dental caries in preschool children is understanding and evaluating the child’s caries risk factors. Previous caries experience and white spot lesions should automatically classify a preschool child as high risk for caries. Microbial factors, such as presence of visible plaque and tests that identify a child as having high levels of mutans streptococci, also predict caries in young children. Frequency of sugar consumption, enamel developmental defects, social factors such as socioeconomic status, psychosocial factors, and being an ethnic minority also have shown to be relevant in determining caries risk. On the basis of this knowledge of specific risk factors for an individual, different preventive strategies and different intensities of preventive therapies can be implemented. Caries preventive strategies in preschool children include fluoride therapy, such as supervised tooth brushing with a fluoridated dentifrice, systemic fluoride supplement to children who live in a nonfluoridated area and who are at risk for caries, and professional topical fluoride with fluoride varnish. There is emerging evidence that intensive patient counseling or motivational interviews with parents to change specific behaviors may reduce caries prevalence in their children. Findings regarding antimicrobial interventions, efforts to modify diets, and traditional dental health education are less consistent.