Hurricane Katrina made landfall on the U.S. Gulf Coast on August 29, 2005. Thousands of Gulf Coast residents evacuated and dispersed across the country, moving into hotels, private homes, and evacuation centers (ECs) in 30 states and the District of Columbia (DC). One goal of public health responders was to identify and prevent hurricane-related morbidity and mortality among affected populations, especially among those with limited access to health care and those who were living in crowded conditions. This report summarizes the challenges of conducting national surveillance after Hurricane Katrina, focusing on the role of CDC in coordinating surveillance and consolidating and interpreting morbidity data from jurisdictions that used diverse surveillance approaches. Aggregate morbidity data that were reported through Arkansas, Louisiana, Mississippi, and Texas to CDC during September 1-22, 2005 (before the Gulf Coast landfall of Hurricane Rita on September 24) are presented from ECs and health-care facilities (HCFs) that served affected populations in these states. Chronic diseases and injuries were the most common conditions reported by ECs and HCFs, respectively. To better prepare for future large-scale disasters with widespread impact, public health agencies and other partners are actively working to establish standardized guidelines and tools for morbidity surveillance. These guidelines will facilitate the interpretation and exchange of health information among multiple jurisdictions and public and private agencies during a disaster response to identify outbreaks and monitor health concerns.