The Brief Pain Inventory is a medical questionnaire used to measure pain, developed by the Pain Research Group of the WHO Collaborating Centre for Symptom Evaluation in Cancer Care. The Brief Pain Inventory (BPI) is widely used around the world today to help with measuring a patients' pain intensity and the amount of interference the pain has on their being able to function in everyday life. BPI was originally intended to help measure cancer patients pain, but today it is used in cancer related cases as well as non-cancer related cases.