Data on caries increments and costs of prevention programs are presented as background information for participants in the workshop. Estimates of annual caries increments were derived from control groups in clinical trials, epidemiologic studies, and national surveys. Cost data were obtained from dental public health directors, program administrators, fluoridation engineers, and water plant operators in different parts of the US. Caries incidence data are reported for age groups: 5-17 years (fluoridated and nonfluoridated areas), 18-44 years, 45-64 years, and 65 and over. Program costs include direct costs primarily and do not allow for program inefficiencies, nor have they attempted to include social costs. All cost data are expressed in 1988 dollars. Direct program costs are included for community water fluoridation, fluoride supplements, fluoride mouthrinses, school fluoridation, and sealant programs. For professionally and self-applied fluoride programs, only material and salary costs are included because total costs could not be located in the literature nor obtained from program directors. All factors and necessary assumptions included in the cost assessments are described.