The initial symptoms and pretreatment in Teheran, Iran, as well as the admittance examination data, the clinical courses of the patients, and the clinical laboratory data in Germany, are reported. The main injuries were to the skin, the eyes, and the respiratory tract. One patient stopped breathing suddenly on the third day of treatment (eight days after the exposure). A large piece of mucous membrane blocking a bronchus was removed during an immediate bronchoscopy, but attempts at resuscitation failed. The most important autopsy findings in this case were severe pseudomembranous inflammation of the trachea and the bronchial tubes. The histological findings are reported. Chemical proof of the poison (mustard gas) was established. A review of the history of chemical warfare, the physical and chemical properties of mustard gas, and a literature survey of clinical findings (including, especially, experiences from World Wars I and II) contribute to the understanding of the actual cases. 31 references and 3 tables (Author abstract)