The author endeavored in this dissertation to trace the development of medieval thought concerning astrology from Augustine to the 15th century, and to interpret references to it in medieval English literature. Contents: ancient astrology; astrology in the early medieval centuries; astrology in Old English literature; Arabian astrology; medieval acceptance of astrology; astrologers in medieval England; astrology in the medieval romances; astrology in Middle English literature; astrology in Gower and Chaucer.