Alchemy and astrology, sometimes dismissed as pseudosciences, were seriously pursued by learned scholars in the Middle Ages. Alchemical texts first came to the Latin West from the Islamic world, but by the 13th century, original Latin treatises were being written. Some show important innovations in matter theory and practical processes. Astrology offered the hope of an anchor in an uncertain world, providing warnings of sickness or danger for individuals, as well as states. This lecture surveys the developments in this often-obscure field.