The American Thoracic Society (ATS) is a nonprofit organization focused on improving care for pulmonary diseases, critical illnesses and sleep-related breathing disorders. It was established in 1905 as the American Sanatorium Association, and changed its name in 1938 to the American Trudeau Society. In 1960, it changed its name again to the American Thoracic Society. Originally the medical section of the American Lung Association, the Society became independently incorporated in 2000 as a 501 (c) (3) organization.