This Bulletin updates the story of world population presented in 1971, "Man's Population Predicament." Estimated at half a billion in 1650, world population reached 2 billion in 1930, 4 billion in 1975, and is projected to be about 6 billion in 2000. Most of today's rapid growth is occurring among people living in less developed countries where the post-World War II gap between high birth rates and falling death rates has only recently begun to narrow. This growth, coupled with high consumption in developed countries, is putting pressures on the resources, environment, and social fabric of the earth. New evidence on Europe's demographic transition and from China, Indonesia, and Thailand in the 1970s suggests that well-designed family planning programs can speed fertility decline but rapid worldwide attainment of replacement-level fertility will also require special development efforts. Current projections for the world's ultimate peak population range from 8 billion in the mid-21st century to 11 billion about 2125, depending on when replacement-level fertility is reached. China's drive for a drastic birth rate reduction and the oil crisis might change fertility behavior more rapidly than most demographers have heretofore thought likely. Numerous graphs and tables illustrate the report. (Author)