Safety analysis and operational experience consistently indicate that human error is the greatest contributor to the risk of a severe accident in a nuclear power plant. Subsequent to the Three Mile Island accident, major changes were made internationally to reduce the potential for human error through improved procedures, information presentation and training of operators. The use of full scope simulators in the training of operators is an essential element of these efforts to reduce human error. In cases where a ‘replica’ plant-referenced full scope simulator is not available, it may be necessary for operators to receive their training with a computer simulation or to travel to another plant that is similar to their plant and has a simulator. This publication has been developed and published to provide information and practical guidance on various aspects of the use of control room simulators, by quoting actual examples from various Member States.