The study of cities, or urban systems, in Industrial Ecology has a peculiar history. In the 1960s, there was a false dawn for green cities in the United States under the Experimental City project, the unfulfi lled plans for which included numerous aspects of Industrial Ecology (IE). When IE eventually began to form as a discipline in the 1990s, cities or urban systems were at best a fringe topic, although their importance was recognized by thought leaders in the fi eld. The development of research on cities as a theme within IE perhaps followed with the broadening of IE to include Social Ecology. Then the study of urban metabolism, which had its own separate literature, arguably became one of the three metabolisms within IE-along with industrial and socioeconomic. In this review of work on IE and cities, a Scopus search of ISI-rated publications fi nds over 200 papers on the topic, many of which are in the Journal of Industrial Ecology. Amongst the common themes are papers on urban industrial symbiosis, urban infrastructure frameworks, transportation, waste, energy, greenhouse gas emissions, other urban contaminants, metals, phosphorus and food in cities. The great ongoing challenge for work on IE and cities remains to understand the environmental impacts related to urban metabolism and attempt to reduce them. More specifi c examples of possible future work include determining potentials for city-scale industrial symbiosis and uncovering how much is occurring and exploring theoretical limits to the sustainability of cities using nonequilibrium thermodynamics.