Early Childhood Caries (ECC), previously called Baby Bottle Tooth Decay and Nursing Caries, is a form of dental caries that affects infants and young children. The often severe disease is difficult and expensive to treatment. Strategies to identify very young children at risk for ECC and rigorous testing of interventions are not well developed. This project has two major components with different research designs; both will determine in certain factors are associated with increased ECC incidence, but will involve very different study populations: A) a population-based retrospective cohort study among 6,058 children born between 1986-1993 to members of the Kaiser Permanente Health Plan in the Pacific Northwest (KPNW) and B) a prospective, randomized clinical trial (RCT) among initially caries-free children under age three at two public health facilities in San Francisco, one serving a primarily Latino and one a primarily Asian population. A) Factors to be assessed from KPNW patient records include information about the child, the parents, the mother (i.e., medications prescribed during pregnancy), the siblings, and the dental providers. Behavioral information (i.e., bottle use, oral hygiene) will be ascertained from questionnaires. Among children born between 1986-90, we will determine if ECC in the primary dentition increases the risk of caries treatment on first permanent molars. B) The RCT will 1) Compare the efficacy of once or twice/year fluoride varnish (FV) application plus counseling to counseling alone in preventing ECC; 2) Assess pre-intervention salivary markers (biologic an chemical), behavioral and demographic factors as predictors of ECC; 3) Compare the efficacy of these interventions between sites serving different ethnic populations with a high prevalence of ECC; and 4) Determine the salivary fluoride release profile from fluoride varnish applied to a sub-set of subjects. If successful, this study will provide methods for targeting children at risk for ECC and evidence that an intervention is efficacious in preventing ECC in this young age group. Collaboration among UCSF, KPNW, the San Francisco public health community and industry will facilitate translation of findings into the dental public health and private sectors.