Chemical weapons continue to pose a serious threat to humanity. With the use of chemical weapons by terrorists in Tokyo, and the projected disarming of the chemical weapon stockpile in this country, the possibility that emergency physicians will encounter patients contaminated by chemical munitions, such as sulfur mustard, exists. Mustard is a vesicating agent with a long latency between exposure and symptoms. Exposure can cause burns, conjunctivitis, pneumonia, and death. We describe 3 workers exposed to mustard at a chemical weapon storage facility. This article reports the first case of an exposure to mustard at a storage facility, as well as the first documented incident occurring in the United States. All physicians who manage patients in an acute care setting should be aware of the presentation and emergency treatments involving patients contaminated with mustard.