Traditionally, risk assessment for environmental chemicals is based upon epidemiological and/or animal toxicity data.Since the release of the National Academy of Sciences Toxicity in the 21st Century: A Vision and a Strategy (2007) and Science and Decisions: Advancing Risk Assessment (2008), there has been a growing interest in incorporating recent advances in technologies and tools into the risk assessment paradigm.Recent developments in computational toxicology, dose response modeling, and high throughput in vitro toxicity testing are providing a basis for advancements in risk assessment technology.These new developments may provide the ability to evaluate many compounds found at contaminated sites throughout the U.S.that have limited or no available toxicity information.In addition, these new methods could also provide supplemental information to traditional in vivo toxicity data analysis.