The only extant copy of Leechbook III occurs in the same manuscript as Bald's Leechbook, Royal 12 D. xvii. All three books were published together in their first edition by Cockayne, although he acknowledged the different (in his words, ‘more monkish’) character of the third book. This third book shares a basic resemblance with the two books of Bald's Leechbook: they all contain medical remedies from Latin and native English sources, are prefaced by a table of contents, and more or less follow a head-to-toe organisational structure (although this structure is much weaker in Leechbook III than in Bald's Leechbook). It is easy to see these texts as three volumes of cures amounting to one very thorough reference text of remedies and information, and, indeed, whoever brought these collections together probably intended them to be used as such.

However, Bald's Leechbook and Leechbook III were most likely originally separate pieces. A colophon follows the two books of Bald's Leechbook, identifying them with the mysterious figures Bald and Cild and separating them from the third book, which follows on immediately from the colophon on the same page. This suggests that the scribe had two exemplars to hand as he or she worked. In keeping with this, Voth has pointed to dialectical dif-ferences between the two collections, and there are also a number of subtler differences between the collections. Leechbook III lacks the thoroughness of Bald's Leechbook. In its two books (one directed towards external ailments and the other internal ailments), Bald's Leechbook contains remedies for a large number of conditions and in many cases lists multiple remedies for a single disease. The collection appears to have been designed as an encyclopaedic medical tool, a detailed reference text for a trained medical practitioner. The third book, on the other hand, is much less comprehensive. It is the shortest of the three books found in the Royal manuscript, spanning only 18 folia (in comparison to the 56 and 52 folia of Books I and II of Bald's Leechbook respectively). The table of contents lists only 76 different chapters and four are missing from the body of the text. Many of the illnesses treated are the same as in Bald's Leechbook.