Research into the effects of extensive reading (ER) in second language acquisition has surged over the past few decades. Many studies report several benefits that come from engaging in ER, including reading rate gains. However, these studies almost exclusively focus on English language learners and tend to be limited by their lack of control over how the ER treatment is conducted. Furthermore, experimental and quantitative studies that investigate the possible effects of ER on the reading skills of learners of Japanese have yet to be fully explored. The goal of this study was to investigate the possible effects of ER on the reading rate development of learners of Japanese as a foreign language. This study also aimed to examine the level of comprehension learners were able to maintain as their reading rates increased as well as the feasibility of a 12,000 character (7,200 standard word) per week reading goal. Finally, this study also surveyed learner perceptions of ER.<br><br>Using a quantitative single-case experiment design, eight intermediate-level learners of Japanese were monitored engaging in ER following strict adherence to ER principles over two and a half to four months. Longitudinal reading rate data as well as reading comprehension, ER, and survey data were collected over the course of the study. Results showed that participants’ reading rates increased significantly following the ER treatment. Furthermore, participants’ comprehension abilities were not hampered by an increase in their reading rates. Results also indicate that a weekly reading goal of 12,000 characters is likely feasible for intermediate-level learners. Finally, it was found that participants had overwhelmingly positive attitudes towards ER. This study provides evidence that ER has the potential to provide a highly enjoyable activity while substantially increasing learner reading rates without hindering comprehension.<p></p>