Purpose: K. Nishi and D. Kewley-Port (2007) trained Japanese listeners to perceive 9 American English monophthongs and showed that a protocol using all 9 vowels (fullset) produced better results than the one using only the 3 more difficult vowels (subset). The present study extended the target population to Koreans and examined whether protocols combining the 2 vowel sets would provide more effective training. Method: Three groups of 5 Korean listeners were trained on American English vowels for 9 days using one of the 3 protocols: fullset only, first 3 days on subset then 6 days on fullset, or first 6 days on fullset then 3 days on subset. Participants' performance was assessed by pre- and post-training tests, as well as by a midtraining test. Results: (a) Fullset training was effective for Koreans as well as Japanese, (b) no advantage was found for the 2 combined protocols over the fullset-only protocol, and (c) sustained "nonimprovement" was observed for training using one of the combined protocols. Conclusions: In using subsets for training on American English vowels, care should be taken not only in the selection of subset vowels but also in the training orders of subsets.