Although it is said that acquiring 4,000-5,000 words are required before entering university, learning vocabulary through textbooks in daily classes is not enough. Most teachers agree that intentional learning of vocabulary is necessary for students. However, there seems to have been no concrete methods about it and it has been thought that vocabulary building depends on students' enthusiasm; so they leave it to their students. In part, it's due to the problem of forgetting. According to the previous researchers, without any revision, most of the words learned are lost from learners' memories. So learners should review new words soon after the initial exposure and then at gradually increasing intervals. It is called expanding rehearsal. Teachers cannot possibly control the intervals for each word, so CALL system is critical on this matter. I have developed an e-Leaming Vocabulary Building System and put it into practice since 2003. The points primarily concerned are that: first, the intake of lexical chunks is significant for functional language use; second, remembering their forms with phonetic aspects is indispensable. Watching my students learn through the system, it has come to light that the system has been working very effectively but some minor changes and a certain syllabus using it are required for its use. I hope this report gives teachers some suggestion towards building students' vocabulary.