The book is concerned with a particular set of Indo-European sounds, the laryngeals, and the effect they had on the sounds, forms and etymologies of the Germanic languages. It contains detailed introductions to all the fundamentals of laryngeal theory, together with an introduction to the problematic history of the laryngeal theory which can be read without specialist knowledge. Research into the Germanic languages has not previously taken account of laryngeal theory, but with it many a sound law, etymology and morphological development can be reformulated or made more precise.