A clear policy message emerges from this study - universal access to health care is fundamental to achieving the goal of health equity. In Thailand, child immunization was distributed uniformly over the economic gradient of mothers or caregivers. Surprisingly, immunization coverage in rural areas and in the children whose mothers or caregivers had no formal education was slightly higher than in urban areas and in those educated beyond secondary school. These findings suggest that better service coverage is provided in rural areas (mainly by district health systems) than in urban areas.