Modern cooperative learning began in the mid- 1960s (D. W. Johnson & R. Johnson, 1999a). Its use, however, was resisted by advocates of social Darwinism (who believed that students must be taught to survive in a "dog-eat-dog" world) and individualism (who believed in the myth of the "rugged individualist"). Despite the resistance, cooperative learning is now an accepted, and often the preferred, instructional procedures at all levels of education. Cooperative learning is being used in postsecondary education in every part of the world. It is difficult to find a text on instructional methods, a journal on teaching, or instructional guidelines that do not discuss cooperative learning. Materials on cooperative learning have been translated into dozens of languages. Cooperative learning is one of the success stories of both psychology and education. One of the most distinctive characteristics of cooperative learning, and perhaps the reason for its success, is the close relationship between theory, research, and practice. In this article, social interdependence theory will be reviewed, the research validating the theory will be summarized, and the five basic elements needed to understand the dynamics of cooperation and operationalize the validated theory will be discussed. Finally the controversies in the research and the remaining questions that need to be answered by future research will be noted.