The Menggu Ziyun 蒙古字韻 (MGZY) is a phonological work produced during the Yuan dynasty (A.D. 1279-1368). Its primary significance is that for the first time Chinese was systematically transcribed into an alphabetic system, the hP'ags-pa script, which enables scholars to study the Chinese phonology of the 13th century with greater precision. The present book is divided into two major sections after the introduction. The first section provides analyses of the hP'ags-pa script, the orthographic principles of the script, and various materials contained in the MGZY. The second part analyzes the phonology of the MGZY from a historical perspective. The Studies on the Menggu Ziyun will be of special interest to Chinese historical phonologists in particular and scholars concerned with the history and culture of China during the Yuan period in general.