Animal products provide one-sixth of human food energy and more than one-third of the protein on a global basis. Much of this comes from the conversion of human-inedible materials to high quality human food. Animal agriculture makes many additional contributions to human well-being, including fiber, draught power and transportation, and nutrient-recycling functions important to the efficiency and sustainability of food production systems. Projections for the future indicate large increases in per capita demand for animal food products, mostly in developing countries. There is strong evidence that increasing foods of animal origin in diets of young children with currently low levels of these foods leads to marked improvement in both physical and mental development. Prospects for the increased feed conversion efficiencies and feed supplies, including feed grains, needed to meet projected demand are discussed. Achieving the increases appears feasible, though not certain. Greater attention on a global basis to maintaining the quantity and productivity of agricultural land, and greater investment in research on both crop and animal production are needed. Ultimately food supply and other aspects of quality of life for all people are very much dependent on how soon and at what level human population is stabilized. (C) 1999 Elsevier Science B.V. All rights reserved.