The use of simulators for the training and qualification of nuclear power plant (NPP) control room operating personnel has become a standard practice throughout the world to develop and reinforce knowledge of plant systems and their relationships. It is an approach to increase the ability to apply plant procedures, to advance practical skills in operating the plant in normal, abnormal and emergency conditions, and to build supervisory skills and teamwork. Simulators are also utilized to conduct the authorization or licensing examinations of control room operating personnel, and there is an increasing trend in the use of simulators for non-training purposes. This publication provides Member States with comprehensive guidance on NPP operator training and describes the use of simulators in training and qualification programmes for the personnel. Current trends in the use of simulators in training programmes, as well as approaches to maintaining and upgrading simulators, are also presented.