In this paper, an integrated approach based on Monte Carlo simulation and Six Sigma methodology is used to analyze the risk associated with a project's total cost. Monte Carlo simulation is applied to understand the variability in total cost caused by the probabilistic cost items. By Six Sigma methodology the range of variation of the project cost can be reduced by operating on the input factors with the greatest impact on total cost to cover the variation of 6 between the limits that were established in the design phase of Six Sigma.