Parameters of simulation models are always subject to uncertainty. In order to reach strong conclusions and solid arguments through simulation, a model should be tested against changes in the parameter values. The sensitivity analysis method should be appropriate for the purpose of the simulation model. System dynamics is a behavior-oriented simulation methodology that aims to explain long-run behavior of the system with feedback loops in its structure. Therefore, in the sensitivity analysis of system dynamics models, sensitivity of the model behavior to the parameter uncertainty should be tested. In this book, Behavior Pattern Sensitivity Analysis, as a simple approach for sensitivity of system dynamics models, is presented. Application of this method to different simulation models are discussed in order to guide the reader through important steps of analysis procedure.