"Great Explorations in Math and Science[R] (GEMS[R]) Space Science" is an instructional sequence for grades 3-5 that covers fundamental concepts, including planetary sizes and distance, the Earth's shape and movement, gravity, and moon phases and eclipses. Part of the "GEMS"[R] core curriculum, "GEMS[R] Space Science" uses the solar system as the focal point for learning. The sequence utilizes models, hands-on investigations, peer-to-peer discussions, reflection, and informational student readings. Students complete four units, each lasting between four and nine sessions. Each unit builds upon knowledge from previous units and can be used independently or in conjunction with one another for an overall learning progression. Two studies reviewed by the What Works Clearinghouse (WWC) investigated the effects of ["GEMS[R] Space Science" on elementary school students. One study (Granger, Bevis, Saka, & Southerland, 2010) is a randomized controlled trial that meets WWC evidence standards without reservations. That study is summarized in this report. The other study does not meet WWC eligibility screens. Appended are: (1) Research details for Granger et al., 2010; (2) Outcome measures for each domain; (3) Findings included in the rating for the general science achievement domain; and (4) Summary of follow-up findings for the general science achievement domain. A glossary of terms is included. (Contains 4 tables, 9 endnotes and 2 additional sources.)