Legislation and regulation are powerful tools for decreasing health risks from environmental hazards. Legislation is enacted by an elected body, and regulations are issued by an agency in the executive branch delegated authority by the legislature to carry out enacted laws. The New York City (NYC) Environmental Public Health Tracking Program makes data and analytic findings available to policy makers to inform development of sound and effective environmental health legislation and regulation. Tracking data and associated science create awareness of environmental hazards and health impacts, guide strategies for mitigating hazards, and sustain support for effective law by documenting beneficial impacts on the environment and health. We describe how environmental and health surveillance data and analytic findings have informed legislation and regulations related to restaurant food safety and air pollution control in NYC. Using data to guide legislative and regulatory processes helps ensure that policy decisions and directions are based on objective evidence.