On September 11, 2001, a total of 343 firefighters from the New York City Fire Department (FDNY) died while responding to the attacks on the World Trade Center

. These firefighters were part of the largest rescue operation in U.S. history, facilitating the evacuation of over 25,000 people

. In the years following the attacks, more FDNY members have died from illnesses related to their exposure at Ground Zero than on the day of the attack itself. Over 360 FDNY personnel have succumbed to 9/11-related health issues, including cancers and respiratory diseases caused by the toxic environment at the site

. Thus, the immediate death toll of firefighters on 9/11 was 343, with additional deaths from related illnesses continuing for decades afterward.