Community college stakeholders are searching with increasing urgency for approaches with the potential to improve the success rates for community college students, particularly those in need of developmental education. "Learning communities," which place cohorts of students together in two or more courses for one semester, are a popular instructional reform community colleges are implementing to improve the outcomes of developmental education students, and have previously been associated with positive social, psychological, and academic outcomes in non-experimental and quasi-experimental research (Engstrom & Tinto, 2008; Stefanou & Salisbury-Glennon, 2002; Tinto, 1997; Tinto, 1998; Zhao & Kuh, 2004). This paper synthesizes results from six random assignment evaluations of developmental education learning communities programs. Five of the six programs were part of the National Center for Postsecondary Research's (NCPR) Learning Communities Demonstration, and the sixth was studied as part of MDRC's Opening Doors Demonstration. The primary question addressed in this study is whether learning communities, compared to "business as usual," lead to better educational outcomes for students who are placed into developmental English and math in community colleges. The authors also examine whether the effects of learning communities vary across colleges and subgroups. (Contains 4 figures, 2 tables, and 6 footnotes.)