This study investigated whether individual differences in learners' age of arrival (AOA) and length of residence (LOR) in a country where a second language (L2) is spoken determine the relationship between L2 perception and production. In the first experiment, 40 Korean learners of English and 10 native English speakers participated in vowel perception and production tasks in English. Results demonstrated that the relationship between perception and production depended on learners' AOA, not LOR. In the second experiment, the same Korean learners of English participated in a vowel perception task in which they judged the accuracy of their own production of English vowels. Results demonstrated that self-perception, or the ability to accurately hear one's own productions, may underlie, at least for some learners, accurate L2 production. Overall, results suggested that self-perception is an important factor in determining the perception-production link and indicated that self-perception may have implications for L2 speech learning. (Contains 7 tables, 1 figure, and 1 note.)