One of the three most important medical herbals composed in Middle English, both in terms of physical length and for the number of species treated, and regularly quoted not only by the editors of the Oxford English Dictionary or the Middle English Dictionary but also by historians of Natural Sciences in Britain since the 1700s, a printed version of the treatise compiled in 1373 by the otherwise unknown Herefordian schoolmaster John Lelamour was surprisingly not yet available to the general public. The present volume fills this gap by offering a critical edition of the text contained in the sole extant copy, together with a detailed introduction discussing such topics as authorship and Quellenforschung, the dialect of the text, or the history of the manuscript; a large collection of explanatory notes which throw light on the textual transmission of the text, translation and copy mistakes, identification of parallel passages, and species identification; a full glosary, and two appendixes, one with the current botanical names of the plants mentioned in the text, and another crossreferencing diseases to the lines in the edition where these appear.