Kitab al-Musta‘ini, or Kitab al-adwiyah al-mufradah (Book of Simples), is a treatise on medical remedies and drugs which draws on the learning of earlier Arab scholars such as Ibn Butlan, Al-Kindi and Al-Biruni, as well as classical Greek authors such as Galen, Dioscorides, Aristotle and Hippocrates. It presents a corpus of knowledge of immense significance to the Medieval world and its execution at a Muslim princely court in Northern Spain in the early twelfth century places it four hundred years ahead of the earliest official pharmacopia in any other European country (the Nuovo receptario of 1499 in Florence). The work was completed by its Jewish author, Yunus ibn Ishaq ibn Baklarish, in AD 1106, and this copy of it was produced only 24 years later, in 1130. This a uniquely important copy of one of the most significant treatises on pharmacology written in Arabic in the Middle Ages. The inclusion of contemporary Latin and Latinized Greek elements, in itself a feature of great rarity, offers compelling evidence of intercultural dialogue fostered by Arab patronage, whilst underscoring the pivotal role of Muslim Spain in the dissemination of medical knowledge throughout the rest of Medieval Europe.