Over the last four decades, community colleges have played an increasingly important role in higher education. Today, community colleges enroll more than one in every three undergraduates nationally. Unfortunately, among students who enroll in community colleges with the intent to earn a credential or transfer to a four-year institution, only 51 percent achieve that goal within six years. Many postsecondary institutions operate "learning communities" to improve low rates of success. Basic learning communities simply co-enroll a cohort of students into two classes together. This report presents results from a rigorous random assignment study of a basic learning community program at Hillsborough Community College in Tampa Bay, Florida. Hillsborough is one of six community colleges participating in the National Center for Postsecondary Research's Learning Communities Demonstration. The demonstration's focus is on determining whether learning communities are an effective strategy for helping students who need developmental education. Appended are: (1) Impact Analyses; (2) Sensitivity Analyses; and (3) Assessment of Syllabi. Individual chapters contain footnotes. (Contains 14 tables, 2 boxes and 3 figures.) [This paper was written with the assistance of Jed Teres and Emily Schneider.]