This study explored whether the association of family income with tooth decay changes with age among children in the United States. A second objective was to explore the role of access to dental health care services in explaining the interrelationships between family income, child age and tooth decay. Data from 7,491 2- to 15-year-old children who participated in the 1999-2004 National and Health and Nutrition Examination Survey were analyzed. The association of family income with the prevalence of tooth decay in primary, permanent and primary or permanent teeth was first estimated in logistic regression models with all children, and then, separately in four age groups that reflect the development of the dentition (2-5, 6-8, 9-11 and 12-15 years, respectively). Findings showed that the income gradient in tooth decay attenuated significantly in 9- to 11-year-olds only to re-emerge in 12- to 15-year-olds. The age profile of the income gradient in tooth decay was not accounted for by a diverse set of family and child characteristics. This is the first study providing some evidence for age variations in the income gradient in tooth decay among children in the United States. © 2012 S. Karger AG, Basel.