Urbanization is one of the most powerful forces influencing global sustainability. It is dominated by three factors: population growth, rural-urban migration and subsequent urban expansion. Perhaps nowhere are these factors more dominant than in developing countries. This volume brings together leading experts including Alan Gilbert, John Friedmann, Saskia Sassen and Janice Perlman to explore the conflicting challenges of rapid urbanization in developing countries. While all have to contend with key issues such as social segregation, poverty, and loss of governability, the ongoing forces of urban growth vary from country to country. By comparing the challenges of urbanization in Africa, Latin America, Asia and the Pacific, this book puts forward a new way of thinking about mega- and million-cities in developing countries - one that promotes their vital function in society as engines of ideas, technologies, societal change, democratic transformation and loci of political will to build a new regime of global sustainability.