It is often recommended that learners not use a dictionary when doing Extensive Reading and instead rely on surrounding context to infer meaning of unknown words. The current research project, supported by a Japanese federal grant, is investigating how access to an integrated dictionary during ER correlates with learners’ ability to accurately guess meaning. Roughly 120 first-year English majors read 200-300,000 words using the ER application Xreading, which offers optional access to glossary definitions. At the beginning and end of the year, students report the reading strategies they use and take a test to gauge their ability to accurately guess meaning from context. This presentation will report results from the first three years of the research project. Results thus far do not indicate overall significant differences between control groups and those allowed dictionary access. Later stages of this research will include further replication and the addition of guessing from context training.