The history of haemophilia shows the human mind attempting to define and encompass a mysterious yet fascinating phenomenon; and also the human heart responding to the challenge of repeated adversity. These responses have not remained isolated but have frequently interacted. As doctors have studied haemophilia in order to try to do more for their patients, their investigations have notably advanced our general understanding of haemostasis; and as haemophiliacs have benefited from improvements in their treatment, they have been eager to help by giving blood samples for experiments as well as in raising funds for research. The mutation giving rise to haemophilia is probably of great age because it occurs in at least three Orders of placental mammals, the Perissodactyla (Ungulata) the Fissipedia (Carnivora), and the Anthropoidea (Primates); for haemophilia has been described in the horse [1] and in nine breeds of dog [2-4] as well as in various races of man. The Orders to which these groups belong may have been distinct from the end of the Cretaceous, say 65 million years ago; and the mutation has probably recurred independently many times, in all three, since it must be nearly lethal in the wild state. The mutation rate in man has been estimated at about 1-4 χ ΙΟ" 5 [5]. Early references The earliest written references to what may have been human haemophilia are attributed to Jewish writings of the 2nd century AD. A ruling of Rabbi Judah the Patriarch exempts a woman's third son from being circumcized if his two elder brothers had died of bleeding after circumcision [6, 7]; and Rabbi Simon ben Gamaliel forbade a boy to be circumcized because the sons of his mother's three elder sisters had died after circumcision (Rothschild 1882 in [8], [9]). There are subsequent similar Rabbinic references; and these features of fatal bleeding after minor surgery in brothers or in maternally related boy cousins are characteristic of the "Opening lecture to the Third European Regional Congress of the World Federation of Haemophilia, London, 17 April 1976, marking the Silver Jubilee of the British Haemophilia Society. 'kind permission of the British Medical Association. disorder we call haemophilia. In the 10th century, males of a certain village who bled to death from trivial wounds were described by Khalaf ibn Abbas, known to us as Albucasis. In the 12th century, Maimonides applied the Rabbinic ruling to the sons of a woman who was twice married [9]: and down the years there are other scattered records of bleeding disorders more or less closely agreeing with the clinical picture we know. The first descriptions which we may say probably do refer to haemophilia are from the end of the 18th century. Although William Hewson, despite his interest in abnormalities of the blood, does not appear to describe the disorder, the anonymous obituarist of Isaac Zoll, writing in 1791 (in [10]), Consbruch in 1793 and 1810 [11], Rave in 1796 [12], and Otto in 1803 [13] all described families in which males suffered abnormally prolonged post-traumat...