The purpose of a scaling system for specific injuries is to provide a common language to facilitate the clinical decisions and the investigative basis for this decision making. This brief overview describes the evolution of the Organ Injury Scaling (OIS) system developed by the American Association for the Surgery of Trauma. The OIS system is based on the magnitude of anatomic disruption and is graded as 1 (minimal), 2 (mild), 3 (moderate), 4 (severe), 5 (massive), and 6 (lethal). To date, the American Association for the Surgery of Trauma OIS system has been developed for visceral and vascular injuries of the neck, chest, abdomen, and extremities. The fundamental objective of OIS is to provide a common language to describe specific organ injuries. The primary purpose of OIS is to facilitate clinical decision making and the necessary research endeavors to improve this process. A good example of this concept is the tumor, node, metastasis classification for solid organ malignancies: a system used worldwide to guide patient care and clinical investigation.