Bloodletting has been part of the history of medicine for more than 2500 years. Up to the end of the Middle Ages, the rationale for bloodletting originated from the ancient greek humoral theory. The great scientific progress from the 16th century and onward, apparently did not weaken its position. Prominent physicians such as Andreas Vesalius (1514-64), William Harvey (1578-1657) and Thomas Sydenham (1624-89) defended bloodletting. In the beginning of the 19th century the use of leeches became the major technique of bloodletting in Europe. In Norway bloodletting was mentioned in royal decrees from the 13th century, and the method became popular in folk medicine. At the end of the 19th century bloodletting came at last to be regarded as ineffective for most of its traditional purposes, and its use declined rapidly. Today, however, bloodletting is being restored in modern medicine as the most effective method of treating the increasing frequent disorders caused by iron overload.