In this chapter it is shown that if an appreciable risk is present in the use of Modelling and Simulation (M&S), Verification and Validation (V&V) should be employed to manage and mitigate that risk. The use of M&S in the domain of critical infrastructure (CI) will always be accompanied by such a risk. It is important that a structured approach to V&V is used in order to be more effective and more efficient than just testing without a clear plan. The Generic Methodology for V&V (GM-VV) is a recommended practise in the international M&S community and adopted by large organisations such as NATO. The GM-VV has a number of concepts that allow for a structured approach to V&V. A structured approach to V&V such as the GM-VV leads to a set of handles that allow the best choices for V&V techniques to employ. The choice for a specific technique is dependent on a number of factors such as the needed certainty, the expected residual uncertainty of the proposed technique and its requirements in terms of costs, real-world knowledge, etc. This chapter is divided in 4 parts. The first part has the take away message “You have to do Verification and Validation because there is risk involved”, the second “You have to do it in a structured way if you want to do it more effective and more efficient” and the third “You have to choose the appropriate Verification and Validation technique to balance risk, effectiveness and efficiency.” In the last part some conclusions are drawn. © The Author(s) 2016.