Summative simulated-based assessments are intended to determine students' competence in practice. These assessments need to be carefully designed and implemented especially when the results are used to make high-stakes decisions.Critical steps need to be followed to design simulations for summative assessment, ensure the validity of the assessment and reliability of the ratings, and train evaluators.Guidelines for using simulation for assessment in nursing are suggested. The guidelines are based on the literature and the authors' experiences from a project that examined the feasibility of using simulation for determining students' competence in performance at the end of the nursing program.Summative simulation-based assessments need to be valid, measuring the knowledge and skills they are intended to, and reliable, with results being reproduced by different evaluators and by the same evaluator at another time. [J Nurs Educ. 2016;55(6):323-328.].