This essay analyzes the known evidence for Byzantine engagement with what are conventionally termed “alchemical” texts, theories, and practices of the Islamic world. Much of the evidence is difficult to date. Nevertheless, the aggregated direct, indirect, and circumstantial evidence suggests at least some engagement by Greek-speaking scholars throughout the Middle Ages. This engagement took various forms, from the use of Arabic, Persian, and Turkish terminology to the adaptation of whole Arabic treatises in Greek. Sometimes the Byzantine texts emphasize their Islamicate (...) sources, and sometimes they do not mention these sources at all. The resulting picture is still fragmentary, but it indicates that medieval Greek-speaking scholars were active in the circulation of chemical knowledge and techniques in the Mediterranean and Middle East. Byzantium, therefore, should no longer be left out of research into long-term patterns in the history of science. (shrink)