Sulfur mustard is one of the major potent chemical warfare agents. It was widely used against not only military personnel but also civilian people ofIranduring the last years (1984–1988) of the Iraq–Iran war. A number of studies were performed regarding the acute and long-term consequences of sulfur mustard on respiratory system. Currently, many aspects of leading respiratory disorder that was prescribed as “mustard lung” have been revealed. However, there is growing concern about pathophysiological mechanisms behind the mustard lung. Herein available published materials about mustard lung are summarized, and it has been tried to highlight practical points relevant to the diagnosis and treatment of the disease.