Abstract
The present study aims to empirically and longitudinally investigate the effects of extensive reading on Japanese EFL high school students with respect to their reading and listening comprehension, and their lexical and grammatical knowledge. The participants chose and read English graded readers outside the class for about eight and a half months and took six kinds of skill and knowledge tests before and after the extensive reading program. The results show that extensive reading of approximately 50,000 words improved the reading comprehension and speed significantly, regardless of the students' level of reading comprehension and speed before the program. Extensive reading also significantly increased the students' word recognition. On the other hand, spelling, grammar, and listening did not improve significantly.
