The aim of the present work is to contribute to the knowledge of Balochi historical grammar. The main part of the book is a new discussion of the historical phonology of Balochi, the only comprehensive treatment of which existing so far dates from the end of the 19th century. Meanwhile, new material from a wide range of Balochi dialects and varieties has come to light. This makes it possible to distinguish between sound changes affecting the Balochi language as a whole and those that operate only in some variety; the approach to do so systematically is attempted here for the first time. Reassessing previous treatments and comparing important related languages (chiefly New Persian, Parthian and Avestan), the book analyses the development of Old Iranian sounds to the stage of Common Balochi and the changes leading from that stage to the variants spoken today in Pakistan, Iran, Afghanistan and some other countries. The results indicate contact with other languages, specifically with Persian, as several Balochi sound changes are not such as we might expect in a North Western Iranian language. Concerning other sound changes, Balochi differs from all attested Middle Iranian languages. The predecessor of contemporary Balochi seems to have been a dialect rather similar to Parthian, but differing from it in a number of details. So the study of Balochi sound changes provides evidence for Middle Iranian dialectal variation. The diversity and intensity of contacts with neighbouring languages is also reflected in the Balochi lexicon of which selected fields are presented and discussed. The layers of loanwords show a continuing influence of Persian from the earliest times to the present day, relationships to Kurdish, Pashto and Brahui, and, particularly in the field of kinship terminology, intense contact with speakers of Modern Indic languages. The book is complemented by a morphological appendix and a comprehensive etymological index. It is intended as a contribution in the fields of New Iranian languages and historical Iranian linguistics.