In many dialects of Japanese, high vowels between voiceless consonants are often devoiced. This devoicing phenomenon is generally considered a phonological assimilation process. It is almost obligatory in theTokyodialect, except for some marked environments in which complete devoicing is often blocked. One such case is so called consecutive devoicing, where two or more consecutive vowels are in devoiceable environments. Although several accounts of consecutive devoicing have been proposed (e.g., Kondo, 2005; Yoshida, 2004; Tsuchida, 1997), the nature of its markedness, namely whether it is phonologically or phonetically driven, is still being debated. In order to provide a more comprehensive account of consecutive devoicing in theTokyodialect, the current study investigated the relative contribution of various factors on its occurrence as well as its across-speaker variability. The results revealed that the manner of consonants surrounding the second devoiceable vowel (C2-C3) had the strongest effect on the likelihood of consecutive devoicing among the factors tested, followed by the quality of vowel in the following mora (V3). Further, large and gradient speaker variability in the occurrence of consecutive devoicing was observed. These results indicate that consecutive devoicing is a phonetically driven process, rather than a phonological process as traditionally considered.