Learning communities at colleges and universities bring together small groups of students who take linked courses together. Interest in learning communities is growing, as is early evidence of their impact on student success. This paper reviews the history and theory underlying learning communities, describes various models, summarizes published research, and describes how some learning communities operate based on field visits to nine colleges. It concludes by proposing a multicollege demonstration project that could produce more conclusive evidence of their effectiveness, and provide information to policymakers and to educational institutions interested in expanding them.