It is often difficult and sometimes impossible to predict the extent of how a variety of factors may impact the outcome of a clinical trial. Modeling and simulation is becoming more common and with increased computing power it is possible to simulate trials under a variety of realistic situations. Simulations can be used to understand traditional operating characteristics such as power and average sample size as well as gain insight into project time lines and when specific milestones may be met during the clinical trial. In this talk I will present a case study of a trial where simulation was used extensively to explore a large number of design possibilities and allow the clinical development team to based design decisions on quantitative information.