Ibn Sina (Latin name – Avicenna, 980–1037) is a famous Muslim physician who wrote The Canon of Medicine. Pain-related writings within The Canon were identified and analysed and compared to Galen and Modern Pain Theory. We found evidence in The Canon that Avicenna challenged Galen's concept of pain. Galen insisted that injuries (breach of continuity) were the only cause of pain. In contrast, Avicenna suggested that the true cause of pain was a change of the physical condition (temperament change) of the organ whether there was an injury present or not. Avicenna extended Galen's descriptions of 4 to 15 types of pain and used a terminology that is remarkably similar to that used in the McGill Pain Questionnaire.