Even though most low income children in the U.S. are entitled to public health insurance, many children are still uninsured. One reason for this problem is that when insurance expires (after, for example, one year of enrollment) parents may fail to re-enroll their child. This report examines rates of renewal in three public health insurance programs in San Mateo County, California: Healthy Families, Healthy Kids, and Medi-Cal. Renewal rates were low in all three programs; only about 50 percent of children renewed coverage after a year. The report provides recommendations regarding improving monitoring systems for tracking retention over time.