this publication is the second in the Research-Based Practices in Early Reading Series published by the Regional Educational Laboratory at Pacific Resources for Education and Learning. Of the many compelling reasons for providing students with instruction to build vocabulary, none is more important than the contribution of vocabulary knowledge to reading comprehension. Indeed, one of the most enduring findings in reading research is the extent to which students' vocabulary knowledge relates to their reading comprehension. The focus of this booklet is on vocabulary instruction as a component of reading comprehension. The booklet does not attempt to address issues related to stand-alone vocabulary building programs and strategies.