Professor Oswald Szemerényi's Einführung in die vergleichende Sprachwissenschaft, first published in 1970, remains the standard introduction to comparative Indo-European linguistics. It is available here in English for the first time, in a revised, enlarged, and updated fifth edition. The introductory section presents a general survey of the principles of diachronic-comparative linguistics, and the remainder of the book is a thorough and detailed analysis, according to those principles, of the phonological and morphological structure of the Indo-European group of languages. Each section of the book has a detailed bibliography, so that the student can progress from the general overview to a more detailed examination of particular topics.