Noting that the amount of reading students do is related to their reading achievement, this booklet presents an instrument designed to measure the amount and breadth of students' reading in and out of school. The first part of the booklet discusses the Reading Activity Inventory (RAI) and how it differs from other reading activity measures, uses of the RAI, and the reliability of the instrument. The second part of the booklet discusses administration and scoring of the RAI and presents the instrument itself. Contains five references. (RS)