"Die Hauptprobleme der indogermanischen Lautlehre seit Bechtel" ("The main problems of Indo-European historical phonology since Bechtel") is the modification of the title of a famous book form the classical period of Indo-European linguistics, Fritz Bechtel´s "Die Hauptprobleme der indogermanischen Lautlehre seit Schleicher" (1892). The development of Indo-European historical phonology between August Schleicher (1821–1868) and Fritz Bechtel (1855–1924) had consisted, above all, in vocalism (dephonologization of I.-E. */e/,*/o/, *a/ to */a/ in Indo-Iranian; the "law of the palatals"), and in the discovery of three consonantal groups in the tectal series. Bechtel (1892) had portrayed the history of comparative phonology in the 19th century; the booklet by Manfred Mayrhofer is dedicated to the development of the same field in the 20th century. The focus is on the "Laryngeal theory" (above all as a creation of Ferdinand de Saussure, Albert Cuny, and, in his early publications, of Jerzy Kurylowicz; with a chapter of the criticisms of the theory´s various forms), and the highly discussed "Glottalic theory", which is connected with many fascinating questions of modern general linguistics.