OBJECTIVE To assess whether expanding public health insurance coverage to parents leads to increases in Medicaid participation among children. METHODS Study uses data from the 1997 and 1999 National Survey of America's Families. Insurance coverage of children eligible for Medicaid under the poverty-related expansions is analyzed. METHODS We conduct two analyses. In the first, we examine the cross-sectional difference regarding whether Medicaid participation is higher for children eligible for Medicaid under the poverty-related expansions when states expand public health insurance programs to cover their parents. In the second, we use a difference-in-difference approach to assess whether the expansion of the Medicaid program to cover parents in Massachusetts led to an increase in Medicaid coverage among children between 1997 and 1999 relative to changes that occurred in the rest of the nation. METHODS The analysis relies on a detailed Medicaid and SCHIP eligibility simulation model that identifies children surveyed on the NSAF who are eligible for Medicaid under the poverty-related expansions. RESULTS Children who reside in states that expanded public health insurance programs to parents participate in Medicaid at a rate that is 20 percentage points higher than of those who live in states with no expansions. The Massachusetts expansion in coverage to parents led to a 14 percentage point increase in Medicaid coverage among children due principally to reductions in uninsurance among already eligible children. CONCLUSIONS Expanding public health insurance coverage to parents has benefits to children in the form of increased participation in Medicaid.