This chapter presents the reading fluency refers to reading speed and it is typically measured in words per minute, or more accurately, in standard words per minute where the number of letter spaces in a text is divided by six. The research shows that extensive reading affects a wide variety of aspects of language proficiency, and in many studies it does this more effectively than intensive reading and traditional language-focused teaching. Measuring the effect of extensive reading on reading comprehension is highly dependent on the difficulty level of the measures used. However, it has the advantages of allowing learners to become familiar with the nature of speed reading and increases reliability by using the average of some measurements. In some of the studies cited, the gains from extensive reading were compared with gains from intensive reading. Oral reading has also been used as a measure, and learners doing extensive reading out-performed intensive reading groups on this measure.