The influential medieval astrologer Sahl b. Bishr was at the center of Baghdad politics and conflict during key years of the 'Abbasid Caliphate, in the early 800s. In this volume, leading astrological translator Benjamin Dykes presents six of his most important works, translated from the Arabic originals into English, including his major Book on Nativities for the first time. Texts here include astrological principles, elections or inceptions, questions or horary, timing techniques, and nativities. The Book on Nativities draws most heavily on the Persian al-Andarzaghar, with extensive passages from Dorotheus, Rhetorius, several books by Masha'allah, and many others. It is one of the textbooks for the traditional astrology course offered by Benjamin Dykes.