The Symphony No. 1 (originally in five movements) was first performed in Budapest in 1889, but the premiere as well as two further performances in Hamburg and Weimar turned out to be a fiasco. After 1894 Mahler removed the “Blumine”-movement. Until the last performance under his direction in New York in 1909, Mahler made revisions again and again. This edition strives to present a, for the performance practice, reliable music text of the final extant version that in 1910 Mahler “corrected and” deemed “accurate for the new print.” The Editorial Report gives detailed information on the provenance and evaluation of the sources as well as authentic annotations on performance practice. Individual comments document editorial interventions and deviations from current editions.