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. More comprehensive learning communities include additional components: The courses have integrated curricula, instructors collaborate closely, and student services such as enhanced advising and tutoring can be embedded, among other approaches. This executive summary 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. Hillsborough's learning communities co-enrolled groups of around 20 students into a developmental reading course and a "college success" course. Three cohorts of students (fall 2007, spring 2008, and fall 2008) participated in the study, for a total of 1,071. The findings show that: (1) The most salient feature of the learning communities implemented at Hillsborough was the co-enrollment of students into linked courses, creating student cohorts; (2) The learning communities at Hillsborough became more comprehensive over the course of the study. In particular, curricular integration and faculty collaboration were generally minimal at the start of the study, but increased over time; (3) Overall (for the full study sample), Hillsborough's learning communities program did not have a meaningful impact on students' academic success; and (4) Corresponding to the maturation of the learning communities program, evidence suggests that the program had positive impacts on some educational outcomes for the third (fall 2008) cohort of students. These results represent the first in a series of impact findings from the Learning Communities Demonstration. Results from the other five demonstration sites will be released in the next several years, providing a rich body of experimental research on the effectiveness of various learning community models in the community college setting. (Contains 4 footnotes.) [This paper was written with Jed Teres and Emily Schneider. For "Learning Communities for Students in Developmental Reading: An Impact Study at Hillsborough Community College," see ED510961.]