In Japanese, "无案内" can be written in the form of "不案内", and pronounced "不(??)案内". It is well known that in Japanese "不" is pronounced in the usual form of Voiceless "?". The questions are: under what conditions and with what words can "无" and "不" be used interchangeably and be pronounced in the form of Voiced "??"? By adopting the approaches of classification and quantitative statistics, the paper divides those Chinese words in The Japanese Dictionary containing the negative prefixes "不" and "无" into three categories: 1. words similar in form but different in meaning; 2. words exclusive to Japanese; 3. pure Chinese words. It also makes a contrastive investigation of those words in The Chinese Dictionary and The Chinese Japanese Dictionary and concludes that the majority of the interchangeably used words containing the negative prefixes "不" and "无" belong to the second category.
