We present a new method of measuring the volume and cross-sectional area of the vocal tract from magnetic resonance images. The vocal tract was divided by the 2 constriction points on the horizontal and vertical planes. The ratios of the volumes of the segment vocal tracts to that of the entire vocal tract play a crucial role in discriminating Korean monophthongs in that vowels were successfully discriminated by the ratios. The discriminant analysis also demonstrated that the acoustic parameters F1 and F2, in addition to the segment volumes, serve as significant parameters in discriminating Korean monophthongs.