In early 2003 San Mateo County, California launched the Children's Health Initiative (CHI), a program to ensure that all children have access to comprehensive health insurance coverage. The report describes the governance structure for the CHI; its financing; enrollment growth (for all three public programs); access to services; use and cost of services for all three public programs; satisfaction on the part of both parents and providers; prior insurance and crowd-out; and the effect the initiative has had on hospital finances. Areas identified as needing attention include improving access to after-hours and dental care; increasing the use of preventive service; and developing new sources of financing for the CHI.