Numerous outbreaks of a disease whose most prominent effects were gangrene and loss of limbs occurred in Europe in the Middle Ages. Sufferers sought relief at the shrine of St Anthony at Vienne in France. Quite early, it was recognized that the disease was a poisoning due to the consumption of bread prepared from rye contaminated with the fungus ergot. Many interesting substances have been isolated from ergot, some of which are used in medicine in migraine and in childbirth, but the most dramatic substance derived from ergot is LSD. The circumstance of some of these discoveries is recounted.