I've updated my article on the environmental Kuznets curve that appeared in the Encyclopedia of Energy in 2004. The revised version will be available as part of Elsevier's Online Reference Database: Earth Systems and Environmental Sciences. I've also posted a working paper version of the article titled: The Environmental Kuznets Curve: A Primer. Despite all the papers that have been published on the topic in the past ten years, I don't think my main messages have changed much. Increases in income tend to increase emissions per capita but time related and other effects can reduce emissions. On the other hand concentrations of some local pollutants are reduced by income increases. The section on theory is a bit more optimistic than I was in 2004 but I think there is still opportunity to develop a comprehensive theory of how income and emissions evolve. I also write in the conclusions that recently developed econometric methods have also only been applied to analyze a couple of well-known pollutants. Therefore, I expect that in coming years this will continue to be an active area of research interest. The emerging issue of how emissions evolve over the business cycle is also likely to be an area of expanding research.