Benefit-cost analysis and cost-effectiveness analysis can be used to evaluate preventive regimens and aid policy-makers in making resource-allocation decisions. This paper demonstrates the application of benefit-cost and cost-effectiveness analyses to preventive dental programs. The two analyses are defined and described, and the purpose of each technic is compared. For a hypothetical community, four dental preventive programs are described: community water fluoridation, school water fluoridation, weekly school-based mouthrinses, and school-based sealants. Benefit-cost ratios and cost-effectiveness ratios are calculated for each program first assuming steady-state conditions, i.e., maximum caries reduction, and then for a 20-year period. Both explicit and implicit costs are included. Underlying assumptions and limitations, as well as the effects of changes in caries rates, differential attack rates, and discount rates on the outcome, are discussed. The analysis reveals that community water fluoridation yields the greatest net benefits and most favorable B/C and C/E ratios. School water fluoridation and mouthrinsing programs are the next most cost-effective, with similar B/C and C/E ratios when the implicit cost of teachers' time is omitted from the calculations. The school-based sealant program yields negative net benefits.