Recordings of read speech in Korean and English were made by native South Koreans and Korean Americans of varying generational status ("second-generation" American-born or "1.5-generation" foreign-born) and analyzed for differences in usage of VOT and fundamental frequency to contrast production of Korean lenis and aspirated stops and affricates. Results show that second-generation Korean speakers, especially females, are not showing the collapse of VOT contrast found in the other two groups, which is part of a sound change nearing completion in Seoul. Female second-generation speakers are also not using f0 to differentiate between the stops to the extent that first- and 1.5-generation speakers are. It is concluded that second generation Korean Americans are not participating in the sound change that their same-age peers in Seoul are, and that second generation and 1.5 generation Korean Americans do not pattern together phonologically as a "heritage speaker" category. The analysis makes a stronger case for applying new models of language acquisition, speech production, and identity formation to heritage language speakers that differ from those used for bilingual speakers.