This study, which originally appeared in the Journal of the American Dental Association, v. 110, no. 5, May 1985, considers the relationship between dental insurance and oral health by examining the effects of different levels and types of cost sharing (coinsurance, deductibles) on oral health. It also investigates the effects of cost sharing on the oral health of different subgroups of the population. In particular, it examines the ways in which cost sharing influences the oral health of the disadvantaged. The results suggest that reducing cost sharing for dental services will improve oral health for those younger than age 35, and especially for subgroups of the population with the poorest oral health. This implies that significant gains in oral health could be expected if coverage were extended to the millions of young adults who are without dental insurance.