This thesis presents an analysis of subjective risk information and participation in the National Flood Insurance Program (NFIP). Data are taken from a survey of residents in flood-prone coastal regions in the southeastern U.S. Regression models are constructed to better understand factors affecting individuals’ perceived risk ambiguity related to flood risk and the role of risk preferences, risk perceptions, and especially risk ambiguity, on the decision to purchase flood insurance. This is the first study not only of the influence of risk ambiguity on NFIP participation, but also of the impact of using different risk perception measures. Results indicate that NFIP participation is significantly affected by mean perceived risk, but the influence of range/variance of perceived risk, which presents one’s perceived ambiguity, is mixed.