SS20. The twentieth volume of the Subsidiary Series is devoted to the largest, and perhaps longest running, multi-volume edition in the Society’s Main Series. Previously consisting of five volumes, published between 1938 and 1956, a sixth volume has been added to Macalister’s edition of Lebor Gabála Érenn in 2009. John Carey already placed the Society and scholars in his debt by providing a New Introduction to Lebor Gabála Érenn in 1993, the inaugural volume of the Subsidiary Series. The five contributors to the present volume, who include the editor, cover an impressive range of ground, from the earliest manuscript version of the text to the latest. Also covered are several  hitherto unexamined sources.