The United States has 51 state health departments and thousands of local health agencies. Their size, structure, and authority differ, but they all possess unique abilities to address obesity. Because they are responsible for public health, they can take various steps themselves and can coordinate efforts with other agencies to further health in all policy domains. I describe the value of health agencies' rule-making authority and clarify this process through 2 case studies involving menu-labeling regulations. I detail rule-making procedures and examine the legal and practical limitations on agency activity. Health departments have many options to effect change in the incidence of obesity but need the support of other government entities and officials