The first textcritical edition of Mahler’s most extensive work is a further milestone in the project, “Mahler – The Symphonies.” The many sources first consulted here for an edition include, among others, the conducting scores used for early performances by Mahler, Mengelberg and other conductors, as well as the parts of the Vienna Philharmonic used by Mahler, Bruno Walter and many additional great conductors right up to the present. Furthermore, another set of parts from Mahler’s personal possession was consulted. These sources, significantly expanding the source base in comparison with that of the 1974 Kritische Gesamtausgabe, guarantee a reliable, scholarly valid music text, shedding at the same time new light on Mahler’s complex process of revision. In unprecedented comprehensiveness, the editorial report contains references from Mahler’s letters and other authentic documents indispensable for an understanding of the work and its interpretation. The orchestral parts feature as usual optimal readability and practicality. Rounding off the edition is the introductory essay “Mahler as Symphonist,” together with the knowledgeable preface by Constantin Floros, doyen of Mahler research.