In our final lecture, we focus on the stars and their patterns in the night sky. Most of the constellations we know today are based on those documented by the 2nd century CE Greek mathematician and astronomer, Ptolemy. The stars were used by sailors to guide their ships and by doctors to treat their patients. Each sign of the Zodiac was associated with specific anatomical regions and with a specific grouping of maladies. Bloodletting, mixing of medicines, and applications of treatments were all thought to be influenced by the stars and the patient’s relationship to them. Like the doctor in Chaucer’s Canterbury Tales, all physicians of those times had to be “grounded in astronomye”. We will explore what that meant and how stargazing and interpretation became a required skill in the medical world.