The snapshots provided by cross-sectional surveys tell us how many children are without health insurance coverage at a point in time and how many of these appear to be eligible for Medicaid but, according to their families’ reports, are not enrolled. What the cross-sectional surveys cannot tell us, though, are the paths that children have taken to becoming uninsured and the paths that most of them will take in becoming insured (again). Nor can the cross-sectional surveys tell us, without considerable measurement error, how much of the uninsurance among children is transitional versus more chronic. Panel surveys such as the SIPP and MEPS can provide such information. By following children and their families over a two-to-three-year period and interviewing them multiple times during the year, these surveys capture transitions between sources of coverage and between insured and uninsured, and they also capture changes in family circumstances that may contribute to the changes that we observe in health insurance coverage. These changes in family circumstances include, most importantly, job loss or re-employment, marriage, and divorce. Smaller changes in income or household composition may also affect Medicaid eligibility and, ultimately, children’s insurance coverage.