Nivkh (formerly called Gilyak) is a language isolate spoken on the island of Sakhalin and on the lower reaches of the Amur River in the Russian Far East. The census of 2002 counts their population as 4,902 of whom only 9.7% regard Nivkh as their mother tongue. This rate is sufficiently low to regard the language as being in danger of disappearance. Since 1997, the author has been engaged in the documentation of this language. This book is a result of his fieldwork to the above-mentioned area. It contains a descriptive sketch of the phonology of Nivkh, and discussions on laryngeal phonology and consonant mutation (lenition). These topics have received a lot of attention in current theories of phonology and the discussions in the last decade have led to substantial progress in understanding these phenomena. This book proposes analyses which succeed in describing complicated phonology on the surface from a restricted number of phonological principles and generalizations. It is aimed to help theoretical phonologists, field linguists and all who want to learn about the phonological system of Nivkh.