This volume offers a reconstruction of the Proto-Ainu language based on the comparative method and internal reconstruction. The book is divided into three parts, the first is dedicated to the reconstruction of Proto-Ainu phonology (vocalism, consonantism, and prosody), the second represents a vocabulary of reconstructed Proto-Ainu lexical items, and the third deals with the problem of the genetic affiliation of the Ainu language. This problem has been approached in the present study from the point of view of the systematic comparisons of reconstructions, not the straight comparisons of the forms attested exclusively in modern languages, which was the major set-back of the previous scholarship on the genetic affiliation of the Ainu language. This volume also includes the nineteenth-century vocabulary of the Kuril Ainu by I. Voznesenskii, previously unknown to the scholars.