Medieval men and women given to the care of the infirm, with both themselves and their patients usually observing religious vows. By 800 the Muslim world had medical hospitals, but W Europe did not in any proper sense until 1200. There were both hospices for the permanently poor, insane, and incurable, and hospitals for temporary medical treatment. One foundation could be both, and often hospitals developed from hospices. Monasteries also became hospitals, while St. Bartholomew's, London, was both. The Rules when observed were Austin, Benedictine, Franciscan, or that of the Knights Hospitallers of St. John of Jerusalem. Diocesan bishops had some control, and the popes bestowed many favors: chapels, cemeteries, indulgences. Laymen also shared in the work, and while the master was sometimes a layman more often he was a religious. The attendant brothers and sisters were mostly nurses, and in larger hospitals were assisted by clerks in minor orders and lay servants.

The eleventh and twelfth centuries saw a huge increase in both hospitals and nursing orders: Antonines, Order of the Holy Spirit, Order of St. William of the Desert, Bethlehemites, Order of St. Catherine, and Beguines and Beghards. The Knights of St. John of Jerusalem, after 1310 known as the Knights of Rhodes, and from 1530 as the Knights of Malta, were exemplary hospitallers. Founded not later than 1108 to care for the sick and provide for pilgrims and crusaders in Jerusalem, they subsequently established and managed hundreds of hospitals and hospices across Europe and the Levant, together with their military efforts. Having conquered Rhodes in 1309, they moved their center there, with the emphasis being more military and their wealth and power much increased after suppressing the Knights Templars in 1312. In 1530 their center became Malta until 1798, and they were reestablished in Rome in 1834.

Hospitallers also served the leper communities and had a great influence on medical progress. Leprosy appeared in Europe about 500 and reached its height in the thirteenth century, declining by 1350 and very rare by 1500. The Hospitallers of St. Lazarus who began to treat leprosy in twelfth-century Jerusalem are but one of many such examples. Most medieval hospitals were very small, fewer than thirty beds, and every country had its great infirmaries: S. Spirito, Rome; Holy Ghost, L├╝beck; St. Leonard's, York. By 1200 also, medieval hospitallers were working under physicians trained at Salerno, Montpellier, and elsewhere, and much documentation testifies to the careful standard of their nursing. The orders flourished well into the modern period, when drastic changes occurred.

R.M. Clay, The Mediaeval Hospitals of England (1909); D. Riesman, The Story of Medicine in the Middle Ages (1935); G. Bottarelli, Storia politica e militare del sovrano ordine di S. Giovanni di Gerusalemme detto di Malta (2 vols., 1940); E.E. Hume, Medical Work of the Knights Hospitallers of St. John of Jerusalem (1940).