"Reading Mastery" is a direct instruction program designed to provide explicit, systematic instruction in English language reading. Reading Mastery is available in two versions, "Reading Mastery Classic" levels I and II (for use in grades K-3) and "Reading Mastery Plus," an integrated reading-language program for grades K-6. The program begins by teaching phonemic awareness and sound-letter correspondence and moves into word and passage reading, vocabulary development, comprehension, and building oral reading fluency. Later lessons continue to emphasize accurate and fluent decoding while teaching students the skills necessary to read and comprehend and to learn from expository text. Lessons are designed to be fast-paced and interactive. Students are grouped by similar reading level, based on program placement tests. This study included both English language learners and English speaking students in grades K-4 in Oregon. The investigators used the "Reading Mastery" program as a supplement to normal reading instruction for Spanish speaking students who were markedly behind expected reading achievement. The What Works Clearinghouse (WWC) reports only the outcomes pertaining to the English language learner subsample. This study found potentially positive effects in the reading achievement domain. (Contains 7 footnotes.) [This publication was produced by the What Works Clearinghouse. The following study is reviewed in this intervention report: Gunn, B., Biglan, A., Smolkowski, K., & Ary, D. (2000). The efficacy of supplemental instruction in decoding skills for Hispanic and Non-Hispanic students in early elementary school. "The Journal of Special Education," 34, 90-103.]