In the Latin Middle Ages, the understanding of the body was significantly influenced by the theory and practice of astrology. The cycles of the body, from birth to death, from health to illness, were assumed to be governed by the cycles of the cosmos. This paper considers the somewhat inchoate doctrines of late medieval medical astrology and these interlocking cycles of life. Since this is, by any measure, a capacious theme, it is illumined by examples taken largely from one source, namely Cambridge, Trinity College MS O.5.26. This manuscript is a large and representative collection of Middle English translations of works on most of the recognised branches of astrology which was probably written some time between 1385 and 1405 that may, one time, have belonged to New College, Oxford. There were two main varieties of medical astrology practiced in the Latin Middle Ages: a lunar medicine which aimed to balance the humours; and a scientific astrological medicine which owed more to the Hellenic and Arabic tradition.