A high variability phonetic training technique was employed to train 26 Mandarin speakers to better perceive ten English vowels. In eight short training sessions, learners identified 200 English vowel tokens, produced in a post bilabial stop context by 20 native speakers. Learners' ability to identify English vowels significantly improved in the training context and in one novel phonetic context. Training did not transfer to a third phonetic context. A delayed posttest indicated that improvement was maintained for one month after training was completed, although in the absence of training, no further improvement was found. Learners' scalar judgments regarding the certainty of their choices on identification tests indicated a significant increase in confidence after training. (Contains 1 table, 2 notes and 6 figures.)