Quantitative analysis is an important tool in chemical engineering practice. It underlies decision making processes, equipment/process design, as well as the understanding of physical/chemical phenomena that occur in chemical industries. Among the foundation of quantitative analysis, mathematics is very important. The main obstacles in applying mathematical approach were due to the complexity of the analytical solution and to the large number of computation needed in the numerical solution. However, since the 1970s, the avability of powerful and fast computational facilities makes the numerical solution more feasible. Hence, mathematical approach becomes more and more powerful and useful. Even though mathematical approaches and calculations are becoming more powerful, however, due to the need of analysis of more complex phenomena, the use of mathematical approaches based on calculus still has limitations. The calculations involing very complicated mathematical equations and/or very large number of computations are still not feasible. Hence approaximation method feasible to be applied to complex phenomena is useful. One of the promosing tools is monte carlo simulation. Even though monte carlo simulation id merely an approximation, not an exact solution, but due to its simplicity, it is very useful and powerful, especially as the basis of engineering judgments as well as for better understanding. The book discesses the applications of monte carlo simulation in chemical engineering cases. Futhermore, to show the accuracies of the simulation, comparison of the results with the ones obtained by other methods are also presented.