This article reviews the history of Third World urbanization, examines the evolution of the urban population from 1970-80 based on the 1st results of the 1980 round of censuses, and examines the prospects for urbanization through the end of the century and the year 2025. From 1910 to World War II the urban population in all Third World countries grew more rapidly than the total population. Both rates of growth were moderate compared to subsequent rates. Total Third World population grew by about .9%/year while the urban population grew at 2.2%/year. From 1950-80 total population grew at 2.2% and the urban population by 4.6%. The urban growth took place in the absence of economic developments capable of explaining or justifying it. Urban growth accounted in large part for the extraordinary increase in cereal importation to the Third World. In 1980 it was estimated that 26.5% of the population if Africa, 63.1% in Latin America, and 25.4% in Asian countries excluding China were urban. A characteristic of third World urbanization is the strong concentration of population in large cities; 43% of the urban population currently lives in cities with population of over 500,000. In Third World market countries, total population growth from 1970-80 is provisionally estimated at 2.5-2.6%/year, while according to UN estimates urban population growth amounted to 4.2%/year and other estimates place population growth amounted to 4.2%/year and other estimates place it at 4.4%/year. The growth of the urban population in China from 1970-80 was estimated at 3.3%/year by the UN. During the 75 years from 1950-2025, the Third World urban population is expected to multiply by a factor of 16, from less than 200 million to over 3 billion. The urban population in 2025 projected by the UN amounts to 837 million in Africa, 724 million in Latin America, and 1.6 billion in Asian market countries, but there is some suggestion that the projection errs on the low side. Increases in food production on the order of 1.9%/year will be required through 2025 to feed the new urban population at the current level. Around the year 2000, cities of 1 million or more will contain about 46% of the urban population and 21% of the total population. The largest Third World cities will continue to grow despite their poor living conditions and lack of economic justification, and the low incomes of the inhabitants will increase the difficulty of improving living standards. Predictions as far ahead as 2025 are hazardous, but it is likely that the rate of growth of the largest cities will have abated somewhat.