Agriculturalists have been benefiting from the range of products and services that trees can supply for thousands of years. Through the integration of trees into agricultural landscapes, farmers and land users at all levels can enjoy diversified production and a range of social, economic and environmental benefits. Agroforestry is the scientific application of this widespread body of knowledge. This stimulating collection explores the experiences of researchers and small-scale farmers undertaking agroforestry development projects around the globe and addresses the question of how local small-scale development successes can be 'scaled up' to create wider, long-term benefits. Each of the contributions offers insights into important wider debates. The relationship between theory and practice, the proper role of research in development, constraints on 'scaling up' local successes, the nature of human motivation for risk-taking and learning, the ways in which individuals and communities respond to technical innovation are all critically explored here. Contributors stress the importance of experimenting with a range of possible agroforestry techniques and approaches, in conjunction with the farming communities that will adopt or reject these methods over time.