There is nothing new under the sun, nor can anyone say: Behold, this is new: for already it was in the old times which were before us.

The survival from periods not too far apart of three more or less complete medical works compiled in Old English – Bald's Leechbook, Leechbook III and the Lacnunga – gives an excellent opportunity to examine how such compilations were made, to find their sources and to see how those sources were used and so to give an insight into the understanding and practice of medicine by the Anglo-Saxons.

It was never the intention of an ancient or medieval medical writer to be wholly original, but rather to reproduce authoritative materials from the past. When an Anglo-Saxon physician or scribe set out to compile a medical collection, he might have had as many as three sources to call upon: Latin works or their translations incorporating the medical lore of Greek, Roman, North African and Byzantine cultures; native northern medicines already in medical compilations; traditional or new remedies never before written down. It is both interesting and instructive to try to trace entries in the surviving Old English texts to these sources, although the attempt can be beset with formidable difficulties. In the first place, because the surviving vernacular medical texts of Anglo-Saxon England are the oldest in Northern Europe, we have no anterior northern material with which to compare them.