The growth theories of the 1950s and 1960s emphasized capital accumulation and technical progress as explanations of growth. More recently theoretical attention has focused on the understanding of progress in terms of learning/human capital (in the tradition of K. Arrow) and investment in research (following H. Uzawa). These newer developments have made some, but only limited, progress. The experience of developing countries suggests that the agenda should be broadened to include the efficiency of factor use, infrastructure (broadly interpreted), and sectoral allocation. These aspects, together with the Kaldorian concern for dynamic increasing returns, provide substantial promise for future research. Copyright 1991 by Royal Economic Society.