Nutrient-efficient crops have an important role in modern agriculture. In the low-input systems that characterize most of world agriculture, nutrient-efficient crops improve crop productivity. In high-input systems of the developed world, nutrient-efficient crops are valuable in reducing pollution of surface and ground water resources from intense fertilization. Recent developments in molecular biology, root biology, rhizosphere interactions, and modeling present new opportunities for the understanding and improvement of crop nutrient efficiency. The degree and extent of nutritional limitations to crop productivity, and the economic and ecological liabilities of intensive fertilization, are such that eventually nutrient-efficient crops will be an important part of integrated nutrient management of cropping systems. [Article copies available for a fee from The Haworth Document Delivery Service: 1–800–342–9678. E-mail address: [email protected]]