▼ This dissertation investigates bilingual language acquisition among children between the ages of 4 and 7, who are raised in the home where both parents speak L1, but they have been exposed to L2 later on during their childhood with some regularity over and above their L1. The focus of this study is the developmental patterns in English and Korean produced by the young Korean-English bilingual children and how they gradually accommodate to two different obstruent systems. Korean and English have different obstruent systems. Korean has an unusual three-way voiceless contrast. Korean has a three-way distinction in both stops and affricates: aspirated, lax, and tense, and a two-way distinction in fricatives: non-tense (aspirated or lax) and tense. All Korean obstruent consonants are voiceless. English has a two-way distinction in stops, affricates, and fricatives: voiceless (the stops are often aspirated) and ‘voiced’ (the stops are usually voiceless unaspirated). The children who participated in this study were 24 Korean-English bilingual children (KEB children), ages 4-7 years old, and 24 monolingual English-speaking and Korean-speaking children (EM and KM children) in the same age range. The bilingual children learned Korean as their L1, but subsequently learned and started to speak English at some point in the age range of 1:6-4:0 years. Subjects looked at a set of pictures to prompt a set of words which contained the target segments in the word-initial position; they were taught what words they should say in English or Korean depending on which language was being tested. They were asked to say the correct word in response to each picture. VOT, stop closure, frication and aspiration durations, total duration, F0, and H1-H2 at the onset of the following vowel were measured. The results showed that the KEB children showed similar phonetic development patterns to the EM and KM children in each language, but they showed slower language acquisition in each language relatively later. The results also showed interactions between English and Korean in the KEB children. In order to distinguish English obstruents from Korean obstruents, the KEB children exaggerated phonetic values of Korean obstruents. Also, some distinct phonetic features of Korean obstruents were found in English obstruents produced by the KEB children, and the KEB children produced less pressed voice for Korean tense obstruents than did the KM children due to the influence of English.