Previous studies on second language (L2) phonetic acquisition in early bilingual learners have mainly examined immigrants to the L2 country; however, with recent growing dual-language immersion programs, the immersed bilingual group emerged and required more attention in the research. This study aims to investigate vowel patterns of young Chinese-English immersed bilingual learners in the domains of perception and production. Of particular interest is how language experience and consonantal context affect their vowel structures in both languages. To explore this, three experiments were conducted. Experiment 1 tested participants' identification of Mandarin and English vowels. Experiment 2 evaluated their perceived similarity of English vowels to Mandarin categories. Experiment 3 examined the acoustic properties of their vowel productions in both languages. The results of the identification task revealed that the immersed bilingual children had relatively stable structures in the perception of Mandarin vowels, but their perceptual organization of English vowels was still developing. In terms of the perceptual assimilation of English to Mandarin vowels, the results showed that the assimilation patterns demonstrated an influence of L2 immersion experience. With respect to production, although the immersed bilingual children established a stable L1 vowel system, their Mandarin vowel production still revealed a potential L2-to-L1 influence. For the production of English vowels, they developed an English-like quadrilateral vowel shape, but some vowel categories were still not distinct from others as compared to the same-aged English-speaking monolingual speakers. With regard to the two effects, the language experience had more evident influence on learners' production and the assimilation patterns as older children usually had different speech performance than younger ones. Finally, consonantal context was found to have a pervasively significant influence on speech production and perception as vowels were usually less identified, occupied different positions in the acoustic space or had different assimilation patterns in the coronal context. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]