Several recent studies have reported an increase in the prevalence of dental fluorosis in the United States, thought to be due to the widespread adoption of various preventive dentistry initiatives using fluoride. Several retrospective studies have found associations between dental fluorosis and these fluoride exposures, especially water fluoridation and fluoride tablets and drops. In this study, a methodology will be developed and implemented for use in longitudinal studies to record dietary and non-dietary fluoride exposures on a 3 month basis in a 'birth cohort' from the time of birth until the age of 3 to 4 years (and in a subsequent study until age 8 years). 1530 mothers with newborns will be recruited from post-partum wards of hospitals. The parents will provide data on infant and childhood exposures and ingestion of fluoride every 3 months during the study, with an additional report at 6 weeks of age (due to frequent feeding habit changes during the first 3 months of life). Data on fluoride intake have not previously been collected in this manner and will be valuable in characterizing the multiple fluoride exposures among infants and young children in the U.S. Composite indexes of exposures to both individual and various combinations of fluoride sources over time will be developed. Total dietary fluoride intake will be estimated. Dental caries and dental fluorosis of the primary teeth will be assessed at age 3 to 4. The distributions of fluoride exposures and intake will be characterized. Multivariate relationships will be investigated among prevalence and severity of primary tooth dental fluorosis and dental caries and the various fluoride exposures. A subsequent study will follow the cohort to age 7 to 8 allowing longitudinal data on fluoride exposures to be collected from birth to age 7 to 8. Then, relationships between primary and permanent tooth dental fluorosis will be assessed and the strength of the associations between the prevalence and severity of permanent tooth dental fluorosis and the "prospectively-collected" data on fluoride exposures would be assessed. The study results will increase current understanding about the delicate balance between the optimal use of fluorides for caries prevention and increased risks of dental fluorosis so that fluoride can continue to be used appropriately for maximum public health caries prevention with minimal risk of dental fluorosis.