This chapter describes Monte Carlo simulation that takes the idea of using statistical trials to get an approximate solution and enables this to be applied to a complex problem. Simulation is a very good technique when it is needed to bring together a lot of data and probabilities. Many of the issues to deal with are too complex to enable them to be easily distilled into a simple mathematical equation or even for them to be governed by an underlying probabilistic structure. In such cases the approach that most companies seek to adopt is Monte Carlo simulation. Monte Carlo simulation takes the idea of using statistical trials to get an approximate solution that can be considered and enables to be applied to a complex problem.