Older youth face many challenges including continuing health care as they approach adulthood. The Affordable Care Act will provide new coverage for young adults. This 10 state study provides new data on Medicaid health costs for youth turning age 18. On average, boys are more expensive than girls at this age. Three groups are particularly high cost, disabled youth enrolled in Supplemental Security Income, foster care youth, and those with behavioral health problems. These three groups account for less than 20 percent of all youth that age, but over half the cost of the program.