Many of the developing world's poorest farmers and food insecure people are highly dependent on root and tuber crops as a contributing, if not the principal, source of food, nutrition, and cash income. Hence, an improved understanding of the production, utilization, trade, and estimated future economic importance of these crops has potentially far-reaching implications for investments in agricultural research at both the international and, perhaps even more importantly, national levels. Previous projections for the evolution of global supply, demand, and trade into the 21st century, however, have focused on grains, oilseeds, and livestock. This paper presents global projections of supply, demand, and trade for root and tuber crops to the year 2020. According to the baseline scenario, roots and tubers will decline in relative economic importance only marginally vis-a-vis the other major food and feed crops over the next three decades. According to an alternative, high demand and production growth scenario, the economic importance of roots and tubers versus the same commodities will increase slightly. The results of this scenario contrast with earlier projections that predicted a decline in importance for roots and tubers. Policymakers should take cognizance of and act on the growth prospects for these crops. In the past, root and tuber crops have often been overlooked in policy deliberations precisely because their potential was considered more limited than actual growth rates clearly indicate, or that current projections foresee. (C) 2000 Elsevier Science Ltd. All rights reserved.