While Mexico City is neither the largest nor the most populated metropolitan area in the world, there are serious environmental threats to its own survival as a viable city, as well as regional and even global spillover effects. While some problems are being addressed, others are deteriorating. This article puts the problems of Mexico City in perspective with respect to 1) population growth and distribution, and their effect on poverty-related environmental problems, 2) the water cycle, deforestation, and subsoil contamination 3) atmospheric pollution by industry and transport. Some of the issues discussed are general to all urbanization processes, while some are exacerbated by the scale of growth in Mexico City or by its specific historical and geographic conditions. It is important to distinguish between the general and localized problems. It is also important to distinguish between poverty-related environmental deprivation and ecological degradation by economic progress.