The pharmacological tradition in the medieval Islamic world developed on the basis of the Greek tradition, with the works of Dioscorides and Galen being particularly popular. The terminology was influenced not only by Greek, but also Middle Persian, Syriac, and indigenous Arabic words. Through recent research into Graeco-Arabic translations, it has become possible to discern the evolution of pharmacological writing in Arabic: in the late eighth century, the technical terms were being developed, with transliterations being used; by the mid-ninth century, many standard Arabic translations for Greek words have been established. Various authors, however, expanded the pharmacology inherited from the Greeks. Galen had established a system of degrees of primary faculties (dry or moist, and warm or cold) that various physicians in the Islamic world modified. Al-Kindī, for instance, invented a theory of how to calculate these degrees in compound drugs, whereas ar-Rāzī criticised the epistemology that underlies Galen's theories. Ibn Sīnā (Avicenna) complemented the various degrees in his description of simple drugs. Furthermore, both Ibn Sarābiyun and al-Kaskarī integrated new drugs from the Islamic heartland, and the Far East into the Greek system. In these ways, the Arabic pharmacology developed in a creative tension of tradition and innovation. © 2011 Copyright Taylor and Francis Group, LLC.