The American Thoracic Society (ATS) is a medical association principally engaged in fostering and advancing clinical and scientific understanding of critical illnesses, pulmonary diseases, and sleep related breathing disorders. The organization is a 15,000-members international society, which represents clinicians, scientists, advocates, and medical educators from health maintenance organizations, long-term care facilities, hospitals and other health care systems. ATS is working on various projects starting from lung transplants and work-related asthma to cystic fibrosis research. Other activities of the society include publishing a journal, The American Journal of Respiratory and Critical Care Medicine, which contains discoveries in basic, clinical, and translational science for improving patient care. AST is headquartered in New York, the US.