This study is the first attempt toward the unified theory of acquisition of Tokyo dialect accentuation by non-native speakers of Japanese and the Japanese speakers of non-Tokyo dialect, i e., speakers from Ibaraki prefecture in Japan. The data are analyzed in regards to the interim accentual system, which is predicted to be produced in the process of the acquisition and be different from that of their mother tongue (dialect) or that of target language (dialect), and which is called interlanguage [ 1] or interdialect [9]. The characteristics of both interlanguage and interdialect was examined and it was found that all subjects seemed to have created the same system under the strong influence of their target language accentual system.