Flemming and Johnson (2007) claim that there is a fundamental distinction between the mid central vowel [?] and the high central vowel [?] in that [?] occurs in an unstressed word-final position while [?] appears elsewhere. Compared to English counterparts, Korean [?] and [?] are full vowels and they have phonemic contrast. The purpose of this paper is to explore the acoustic quality of two English reduced vowels produced by Korean learners and native speakers of English in terms of their two formant frequencies. Sixteen Korean learners of English and six native speakers of English produced four types of English words and two types of Korean words with different phonological and morphological patterns. The results show that Korean learners of English produced the two reduced vowels of English and their Korean counterparts differently in Korean and English words.