Most of the world's population now lives in urban areas, and in developing regions the proportion living in cities and towns has risen from 35 percent in 1990 to 45 percent in 2010, from 1.4 billion to 2.5 billion people (Jacobsen et al. 2012). A 2008 World Bank analysis estimated that a third of people living on less than US$2 per day reside in urban areas, and United Nation or UN-habitat estimates that just under 40 percent of urban dwellers live in slums, a number that is growing by more than 20 million per year (Baker 2008). These disparities highlight a pressing need to address the urban sanitation challenge comprehensively, with emphasis on including slum dwellers and poor communities that have typically been neglected. Without concerted intervention, the prospects of cholera, diarrhea, and worm infections will increase, jeopardizing education, productivity, and the quality of life for all urban dwellers. Although this overview of urban sanitation has shown that the current situation is far from ideal, and that widespread improvements will not occur at the present rate of progress, it also identifies initiatives that have potential for wider replication. There is no 'silver bullet' that will deliver improved sanitation to the developing world's burgeoning cities, and some key technical issues remain to be resolved, but much can be achieved by applying what is already known and proven in practice.