The "Read Naturally[R]" program is a supplemental reading program that aims to improve reading fluency, accuracy, and comprehension of elementary and middle school students using a combination of texts, audio CDs, and computer software. The program uses one of four products that share a common fluency-building strategy: "Read Naturally[R] Masters Edition," "Read Naturally[R] Encore," "Read Naturally[R] Software Edition," and "Read Naturally[R] Live." The common strategy includes: modeling of story reading, repeated reading of text for developing oral reading fluency, and systematic monitoring of student progress by teachers and the students themselves. Students work at their reading level, progress through the program at their own rate, and work (for the most part) on an independent basis. The program can be delivered in three ways: (1) students use audio CDs with hard-copy reading materials ("Read Naturally[R] Masters," "Read Naturally[R] Encore"), (2) students use the computer-based version ("Read Naturally[R] Software Edition"), or (3) students use the web-based version ("Read Naturally[R] Live"). This intervention report includes studies of "Read Naturally[R] Masters Edition" and "Read Naturally[R] Software Edition." The What Works Clearinghouse (WWC) identified five studies of "Read Naturally[R]" that both fall within the scope of the Beginning Reading topic area and meet WWC evidence standards. Four studies meet standards without reservations, and one study meets WWC evidence standards with reservations. Together, these studies included 484 beginning readers in grades 2-4 in more than 14 locations. The WWC considers the extent of evidence for "Read Naturally[R]" on the reading skills of beginning readers to be small for two outcome domains--alphabetic s and general reading achievement--and medium to large for two outcome domains--comprehension and reading fluency. (See the Effectiveness Summary on p. 5 for further description of all domains.) "Read Naturally[R]" was found to have no discernible effects on alphabetics and comprehension, mixed effects on reading fluency, and potentially positive effects on general reading achievement for beginning readers. The WWC identified 58 studies that investigated the effects of "Read Naturally[R]" on the reading skills of beginning readers. The WWC reviewed 11 of those studies against group design evidence standards. Four studies (Arvans, 2010; Christ & Davie, 2009; Hancock, 2002; Kemp, 2006) are randomized controlled trials that meet WWC evidence standards without reservations, and one study (Heistad, 2008) is a quasi-experimental design that meets WWC evidence standards with reservations. Those five studies are summarized in this report. Six studies do not meet WWC evidence standards. The remaining 47 studies do not meet WWC eligibility screens for review in this topic area. Citations for all 58 studies are provided in the References section. A summary of studies meeting WWC evidence standards without reservation are as follows. (1) Arvans (2010) conducted a randomized controlled trial of second- through fourth-grade students from one Midwestern elementary school. Students were randomly assigned to intervention and comparison groups using block randomization procedures. Students were paired based on pretest scores, grade, race, and gender, and then randomly assigned to either the "Read Naturally[R]" group or the comparison group. Students in the comparison group received their classroom's normal reading instruction. The final analysis sample consisted of 82 students. (2) Christ and Davie (2009) randomly assigned 109 third-grade students from six schools in four Midwestern school districts to either a "Read Naturally[R]" group or a comparison group. Students were deemed eligible for the study if they scored at or below the 40th percentile on measures of oral reading fluency and reading comprehension. Students in the comparison group received their classroom's normal reading instruction, with no supplemental fluency instruction. The analysis sample consisted of 106 students. (3) Hancock (2002) conducted a randomized controlled trial of second-grade students in five classrooms from one school in Arizona. Students were randomly assigned to intervention and comparison groups using block randomization procedures. Students were pretested, matched with a similarly-performing peer in their classroom, and then randomly assigned to either the intervention group or the comparison group. Forty-eight students were in the "Read Naturally[R]" group, and 46 students were in the comparison group, which received a supplemental mathematics intervention. (4) Kemp (2006) conducted a randomized controlled trial of third-grade students in three schools in a school district in Orange County, California. From 13 study classrooms, an initial sample of 168 students was randomly assigned to intervention and comparison groups using block randomization procedures. Within each classroom, students were assigned to pairs based on their scores from the reading portion of the California Standards Test from the previous spring. One member from each pair was randomly assigned to the intervention group, and the other member was randomly assigned to the comparison group. Comparison students participated in structured sustained silent reading; these reading sessions occurred concurrently with sessions of "Read Naturally[R]." The final analysis sample consisted of 158 students. A summary of one study meeting WWC evidence standards with reservations is as follows. Heisted (2008) examined the effects of "Read Naturally[R]" on the reading achievement of third-grade students who were enrolled in elementary schools in the Minneapolis Public School District. Students in three "Read Naturally[R]" elementary schools that were implementing "Read Naturally[R]" were matched with comparison students from other schools in the same district based on pretest score, grade, demographic variables, and the Adequate Yearly Progress (AYP) status of their school. "Read Naturally[R]" was implemented as a supplemental reading intervention with individual and small groups of students. Two schools implemented "Read Naturally[R]" as a pull-out intervention during the school day, while one school used it as part of an after-school program. Students in the comparison group attended schools that were not implementing "Read Naturally[R]." A total of 44 students were included in the study's analysis, with 22 students in each of the intervention and comparison groups. The following are appended: (1) Research details for Arvans, 2010; (2) Research details for Christ and Davie, 2009; (3) Research details for Hancock, 2002; (4) Research details for Kemp, 2006; (5) Research details for Heistad, 2008; (6) Outcome measures for each domain; (7) Findings included in the rating for the alphabetics domain; (8) Findings included in the rating for the reading fluency domain; (9) Findings included in the rating for the comprehension domain; (10) Findings included in the rating for the general reading achievement domain; (11) Supplemental subtest findings for the alphabetic domain; and (12) Supplemental subtest findings for the comprehension domain. A glossary of terms is included. (Contains 11 tables and 10 endnotes.)