This study investigated reading comprehension, reading fluency and attitudes of students after exposure to extensive reading (ER), an approach to teaching and learning foreign languages without using a dictionary or focusing on grammar, but aiming to get learners to read extensively by choosing books on their own, for general comprehension, good reading habits and enjoyment (Day and Bamford 1998; Prowse 1999). It was conducted in the Thai context with English as foreign language (EFL) students at Rajamangala University of Technology Thanyaburi (RMUTT) in Thailand during a period of four months, one academic semester. The teaching procedure conformed to the principles of ER with a wide-ranging selection of graded reader books. Multiple measurements used to assess comprehension with three narrative texts were written recall protocol, and translation tests; multiple choice questions with twelve texts in timed reading to assess reading fluency; and a survey questionnaire as well as an in-depth interview to gather data on attitudes towards extensive reading. The study employed a double-control pre- and post-test (Solomon) design: two experimental groups (N = 52 and 50) and four control groups (N = 46, 48, 42, and 46) of which two are excluded from the pretest to separate out the effects caused by using the same instruments. The findings suggest positive effects of ER on the learners’ reading comprehension and provide conclusive evidence of reading fluency improvement together with a positive attitude towards ER. The study also revealed that credit or score is a key factor to encourage students to read and they preferred reading in a controlled situation in class including taking the tests of timed reading. The thesis discusses the possibility of using testing as a pedagogical tool for the improvement of reading skills. Implications drawn from the findings suggest that in order to maximize the benefits of ER, an adjustment of procedures is essential prior to the integration with language courses in the Thai and other similar contexts.