The major challenges of project risk assessment may be attributed to the knowledge requirements for determining the level of uncertainty and the development of complex models to predict project outcomes. The duration-cost influence network is an adequate model that can be used for activity-based risk modeling. In this study, a scenario analysis feature is added to this model and a Web-based tool is developed that can be used to calculate risk-adjusted duration and cost, considering the risks affecting cost and duration of individual activities. Monte Carlo simulation is used to create scenarios, and the output of these scenarios is calculated by using the cost-duration influence system that simulates the vulnerability of the project to the identified risk factors. The Web-based tool can be used by decision makers during the preplanning stage of construction projects to estimate the cost and duration implications of various risk occurrence scenarios, determine contingencies, and prepare risk-management plans. DOI: 10.1061/(ASCE)CO.1943-7862.0000547. (C) 2012 American Society of Civil Engineers.