This study compares the underlying perceptual structure of vowel perception in monolingual Chinese, monolingual English and bilingual Chinese-English listeners. Of particular interest is how listeners' spatial organization of vowels is affected either by their L1 or their experience with L2. Thirteen English vowels, /i, I, e, epsilon, ae, u, omega, o, (see symbol), alpha, (see symbol)I, alphaI, alphaomega/, embedded in /hVd/ syllable produced by an Ohio male speaker were presented in pairs to three groups of listeners. Each listener rated 312 vowel pairs on a nine-point dissimilarity scale. The responses from each group were analyzed using a multidimensional scaling program (ALSCAL). Results demonstrated that all three groups of listeners used high/low and front/back distinctions as the two most important dimensions to perceive English vowels. However, the vowels were distributed in clusters in the perceptual space of Chinese monolinguals, while they were appropriately separated and located in that of bilinguals and English monolinguals. Besides the two common perceptual dimensions, each group of listeners utilized a different third dimension to perceive these English vowels. English monolinguals used high-front offset. Bilinguals used a dimension mainly correlated to the distinction of monophthong/diphthong. Chinese monolinguals separated two high vowels, /i/ and /u/, from the rest of vowels in the third dimension. The difference between English monolinguals and Chinese monolinguals evidenced the effect of listeners' native language on the vowel perception. The difference between Chinese monolinguals and bilingual listeners as well as the approximation of bilingual listeners' perceptual space to that of English monolinguals demonstrated the effect of L2 experience on listeners' perception of L2 vowels.