The overall purpose of this project is twofold: (1) to develop a model of people's intuitive understanding of chemical risks and toxicological principles; and (2) to compare this model with that of expert toxicologists and risk assessors. Specific objectives of the study are (1) to develop a better understanding of how laypersons and experts assess toxicological risks, (2) to investigate differences in risk perceptions within the expert and lay communities, and (3) to conduct empirical studies that examine the knowledge base and conceptual frameworks used by experts and laypeople to assess chemical risks. Despite the importance of understanding public perceptions of chemical risks, little research has been directed toward this end. This innovative study will provide information important to both risk analysts and decision makers. Specifically, it will clarify the nature of the cognitive frameworks used by laypersons and by experts to assess risks. It will also contribute to the development of more effective risk communication about the risks and benefits of chemical hazards.