Articulatory variation due to the production of vowels at five pitch frequency (F0) levels (110 Hz, 123 Hz, 130 Hz, 146 Hz, and 164 Hz) was analyzed by volumetric magnetic resonance imaging (MRI). Three Japanese male subjects produced sustained Japanese vowels /a/ and /i/. Observation of vocal tract area functions extracted from the MRI data revealed that F0 shift in vowel production affects not only the length of the vocal tract but also its shape. Analysis employing coefficient of variation for lengthnormalized area functions revealed that the shape of the vocal tract does not change proportionately by F0 shift and that each subject adopt different strategies for controlling F0 while maintaining the phonetic identity of the vowel.