Concern about agricultural sustainability emerged as a major issue in the closing decades of the last century as part of the global debate about the sustainability of economic development. In the 1980s, the three pillar concept of sustainable development was proposed and specifically applied by Conway to the evaluation of alternative agroecosystems. Although Conway’s contribution was important at the time, it was limited in its perspective. Recent approaches adopt a wider approach, and in this century, attention has been focusing on ways to sustainably increase agricultural supplies rather than to just maintain these. This recognizes the fact that a substantial increase in demand for agricultural produce is expected in this century. Consequently, the scope and rationale for sustainably intensifying agriculture is examined (in some detail), and the extent to which greater use of organic agriculture is able to contribute to sustainable agricultural development is assessed. The comparative roles of agroecology and economics in guiding agricultural production are discussed, and the concept of multifunctional agriculture is re-examined in the light of proposals for the sustainable intensification of agriculture. Important shifts in the debate about agricultural sustainability have occurred in this century.