This United Nation's publication presents data on the size and growth of urban and rural populations for all countries of the world and contains revised estimates and projections for all urban agglomerations that had at least one million inhabitants in 1990. Chapter 1 presents levels of urbanization and future trends for urban and rural populations in the world. Chapter 2 describes the world's largest urban agglomerations according to population size, their regional distribution, and prospects for their future growth. The subject of chapter 3 is a focus on urban structure and hierarchy. Chapter 4 provides the sources of data that underlie the estimation of urban population including each country's definition of urban population and statistical concepts used in estimating national capitals and urban agglomerations. The final section contains 16 annex tables that provide a wealth of detail about the characteristics of urban and rural populations and urban agglomerations from 1950-2025. (CK)