Editors' Summary: Risk assessment is one tool of legal and policy decisionmaking, and one that may play a large role in establishing nanotechnology policy and regulations. In this Article, Jonathan Gilligan analyzes different methods of risk assessment and applies these methods to nanotechnology. Gilligan challenges the notion that people perceive and react to risk in a logical way, postulating that both experts and laypeople are susceptible to irrationality when it comes to risk perception. He concludes with a determination that a singular approach to risk management of nanotechnology may not be enough; rather, multiple risk management methods should be utilized depending on qualitative assessments of different nanotechnologies.