The lung is an extremely complex organ and participates in initial responses to inhaled antigens, infectious agents, and irritants or as a response to exposure through the oral, parenteral, or transdermal routes. There can be constriction of the airways or involvement or even destruction of the lung parenchyma, depending on the condition. This review focuses on selected aspects of the pulmonary innate and adaptive immune responses; the new condition World Trade Center cough, which can cause an asthma-like presentation and resemble reactive airways dysfunction syndrome; and the diagnosis and treatment of various immunologic lung conditions. Innate immune responses occur in the acute respiratory distress syndrome and in transfusion-related acute lung injury. Adaptive immune responses involve specialized mucosal and systemic immune responses, lymphocytes, and antibodies and can result in CD4⁺ T_H1 and T_H2 phenotypes, such as T_H1 for tuberculosis and T_H2 for asthma.