This study is the sixth in the series "Studies in the Phonology of Asian Languages." A phonetic and phonemic analysis of the three complex nuclei of Vietnames (Hanoi dialect), spelled (1) ye-, -ie-, -ia, (2) -u'o'-, -u'a, and (3) -uo-, -ua, was carried out using the sound spectrograph. The relative domains of the target qualities of the complex nuclei were established and then compared with those of the eleven simple vowels. Further analysis was done, varying the environment with regard to type of syllable, tone, and initial and final consonants. Regardless of environment, a relative distincitiveness of domain seems to be maintained. (Author/DD)