This systematic review draws from and builds upon the results of a meta-analysis of the achievement effects of three types of interaction treatments in distance education: student-student, student-teacher, and student-content (Bernard et al., "Review of Educational Research," 79(3), 1243-1289, 2009). This follow-up study considers two forms of student-student interaction treatments, "contextual interaction" and "designed interaction". Typical contextual interaction treatments contain the necessary conditions for student-student interaction to occur, but are not intentionally designed to create collaborative learning environments. By contrast, "designed interaction treatments" are intentionally implemented collaborative instructional conditions for increasing student learning. Our meta-analysis compared the effect of these two types of interaction treatments on student achievement outcomes. The results favored designed interaction treatments over contextual interaction treatments. Examples of designed interaction treatments and a discussion of study results and their potential implications for research and instruction in distance education and online learning are presented. (Contains 3 tables.)