This publication deals with programs of infrastructure risk. The objective, exploring different methodologies and related applications, recognized four major topics: Complex Models; Simulation Models; Distributional Models; and Deterministic Models. Focus is on the following issues: the state-of-the-art and practice, gaps between the arts and practices, ways to bridge the gaps, and future research directions. In the first chapter, papers can be found on Computational Nonlinear Models of Risk Assessment, Risk-Based Evaluation of Safety and Security Programs in Critical Infrastructure and Risk Assessment of Modes of Terrorist Attack. One of the papers in the chapter on Simulation Models is on Computational Models for the Simulation of Evacuations following Infrastructure Failures and Terrorist Incidents."Bayesian Belief Nets for Discrete and Continuous Variables" and "Development of Risk Based Software for Analysis of Power Engineering Accidents" are two titles of papers in the third chapter of the book on Distributional Models. Finally, the fourth chapter on Deterministic Models focuses on Environmental Risk Ranking and more.