"Reading Mastery," one of several curriculum components that constitute the "Direct Instruction" program from SRA/McGraw-Hill, is designed to provide systematic instruction in reading to students in grades K-6. "Reading Mastery," which can be used as an intervention program for struggling readers, as a supplement to a core reading program, or as a stand-alone reading program, is available in three versions: (1) "Reading Mastery Classic" (for grades pre-K-3); (2) "Reading Mastery Plus" (for grades K-6); and (3) "Reading Mastery Signature Edition" (for grades K-5). During the implementation of "Reading Mastery," students are grouped with other students at a similar reading level, based on program placement tests. The program includes a continuous monitoring component. This review of "Reading Mastery" for Beginning Reading focuses on students in grades K-3. No studies of "Reading Mastery" that fall within the scope of the Beginning Reading review protocol meet What Works Clearinghouse (WWC) evidence standards. The lack of studies meeting WWC evidence standards means that, at this time, the WWC is unable to draw any conclusions based on research about the effectiveness or ineffectiveness of "Reading Mastery" on beginning readers in grades K-3. Additional research is needed to determine the effectiveness or ineffectiveness of this intervention. The WWC identified 166 studies of "Reading Mastery" for beginning readers that were published or released between 1983 and 2012. Thirty-four studies are within the scope of the Beginning Reading review protocol but do not meet WWC evidence standards. Eighty-four studies are out of the scope of the Beginning Reading review protocol because they have an ineligible study design. Forty-eight studies are out of the scope of the Beginning Reading review protocol for reasons other than study design. A glossary of terms is provided. (Contains 2 endnotes.)