Abstract
This study investigated the relationship between learners' vocabulary size and reading comprehension of academic texts. A reading comprehension test from the National Center Test and an online vocabulary size test were administered to 177 preintermediate Japanese EFL university students. The findings showed that (1) 3,000 words from the JACET List of 8,000 Basic Words covered 95% of the words used in the National Center Test reading section, and (2) an estimated vocabulary size of 5,000 words is needed to score reasonably in National Center Test reading comprehension. However ,these findings are possibly explained by a recognition that the threshold level is not an all-or-nothing boundary, but a probabilistic boundary.
