The purpose of this study is to investigate how important Korean high school students perceive English word stress to be, how familiar they are with word stress, and how well they pronounce the reduced vowel /ə/. Sixty high school students in Seoul participated in a survey study that investigated their perception of the importance of word stress in English. They were then asked to mark the stress on each of the 44 words selected from the basic vocabulary list compiled by the Korean Ministry of Education and to pronounce each word twice. The results of the survey revealed that a vast majority of the students (50 out of 60, 80%) do not pay attention to the stress and pronunciation of words when they study new vocabulary and that they memorize only the spelling and meaning of new words. As a result, many of them could not identify the stressed syllables in many of the 44 words, even when they knew their meaning. As for their pronunciation of the reduced vowel /ə/, the students on average were able to pronounce /ə/ correctly in only 23 words, although they stressed the correct syllable in 28 words. All these results highlight the necessity of teaching Korean students explicitly the importance of word stress in English and the correct pronunciation of the reduced vowel /ə/ in order to help them improve their intelligibility.