Problem/ConditionAfter the September 11, 2001, terrorist attacks on the United States, approximately 400,000 persons were exposed to toxic contaminants and other factors that increased their risk for certain physical and mental health conditions. Shortly thereafter, both federal and nonfederal funds were provided to support various postdisaster activities, including medical monitoring and treatment. In 2011, as authorized by the James Zadroga 9/11 Health and Compensation Act of 2010, the CDC World Trade Center (WTC) Health Program began providing medical screening, monitoring, and treatment of 9/11-related health conditions for WTC responders (i.e., persons who were involved in rescue, response, recovery, cleanup, and related support activities after the September 11, 2001, terrorist attacks) and affected WTC survivors (i.e., persons who were present in the dust or dust cloud on 9/11 or who worked, lived, or attended school, child care centers, or adult day care centers in the New York City disaster area).Reporting Period Covered2012–2020.Description of SystemThe U.S. Department of Health and Human Services WTC Health Program is administered by the director of CDC’s National Institute for Occupational Safety and Health. The WTC Health Program uses a multilayer administrative claims system to process members’ authorized program health benefits. Administrative claims data are primarily generated by clinical providers in New York and New Jersey at the Clinical Centers of Excellence and outside those states by clinical providers in the Nationwide Provider Network. This report describes WTC Health Program trends for selected indicators during 2012–2020.ResultsIn 2020, a total of 104,223 members were enrolled in the WTC Health Program, of which 73.4% (n = 76,543) were responders and 26.6% (n = 27,680) were survivors. WTC Health Program members are predominantly male (78.5%). The median age of members was 51 years (interquartile range [IQR]: 44−57) in 2012 and 59 years (IQR: 52−66) in 2020. During 2012−2020, enrollment and number of certifications of WTC-related health conditions increased among members, with the greatest changes observed among survivors. Overall, at enrollment, most WTC Health Program members lived in New York (71.7%), New Jersey (9.3%), and Florida (5.7%). In 2020, the total numbers of cancer and noncancer WTC-related certifications among members were 20,612 and 50,611, respectively. Skin cancer, male genital system cancers, and in situ neoplasms (e.g., skin and breast) are the most common WTC-related certified cancer conditions. The most commonly certified noncancer conditions are in the aerodigestive and mental health categories. The average number of WTC-related certified conditions per certified member is 2.7. In 2020, a total of 40,666 WTC Health Program members received annual monitoring and screening examinations (with an annual average per calendar year of 35,245). In 2020, the total number of WTC Health Program members who received treatment was 41,387 (with an annual average per calendar year of 32,458).InterpretationSince 2011, the WTC Health Program has provided health care for a limited number of 9/11-related health conditions both for responders and survivors of the terrorist attacks. Over the study period, program enrollment and WTC certification increased, particularly among survivors. As the members age, increased use of health services and costs within the WTC Health Program are expected; chronic diseases, comorbidities, and other health-related conditions unrelated to WTC exposures are more common in older populations, which might complicate the clinical management of WTC-related health conditions.Public Health ActionAnalysis of administrative claims data in the context of WTC research findings can better clarify the health care use patterns of WTC Health Program members. This information guides programmatic decision-making and might also help guide future disaster preparedness and response health care efforts. Strengthening the WTC Health Program health informatics infrastructure is warranted for timely programmatic and research decision-making.