<p>In the past half-century, megacities of more than 10 million people have become a global phenomenon. The need for urban metabolism studies in these giant cities is critical because they consume a disproportionate share of the world's resources. However, the full extent to which the urban metabolism has been documented in megacities is largely unknown. In this paper, we take stock of the metabolism literature in megacities and search for geographical and historical themes therein. We procured more than 100 English-language studies on the energy, material, waste, and water flows in the world's biggest cities, and through review and synthesis of this work, we extracted three generalizations. First, the metabolism of megacities has been investigated for changes across temporal scales (diurnal, monthly, annual), which testifies to the dynamic nature of urban energy and material flows. Second, the metabolism of megacities is equally well documented for changes across spatial scales (local, regional, global), revealing disparities in resource flows and quality of life within and among megacities. Third, literature on the metabolism of megacities in low/middle income regions is characteristically recent, with much of the research produced in the past 10 years and focused primarily on municipal solid waste. The role of the informal sector to help reduce solid waste flows is an important subtheme of that literature. This review will enhance understanding and awareness of the urban metabolism — especially in low/middle income regions—and help to facilitate research into sustainable urban development in megacities. Keywords: urban metabolism, megacity, energy, utilities</p>