It would be nearly impossible using current methods to test all the chemicals in use for toxic effects. So how do we prioritize which ones to study? In this podcast, Martyn Smith describes how he and his colleagues are developing lists of “key characteristics” shared by toxicants that cause specific adverse health effects, such as cancer or male or female reproductive toxicity. Risk assessors can use this information to predict the toxicity of other chemicals in an organized, systematic way. This approach may be useful in prioritizing chemicals for more detailed evaluation. Visit the podcast webpage to download the full transcript of this podcast.