The purpose of this volume is to look at the developments and changes that have occurred in the area of mental workload and its assessment since the NATO symposium was held in 1979. This has been achieved by inviting prominent researchers to survey their respective areas of expertise.Examined are the current methodologies, individual differences, unanswered questions, and future directions for the mental workload issue. Particular topics discussed include the properties of workload assessment techniques, physiological measures, heart rate variability, effort and fatigue in relation to the workload experienced during normal daily routines, subjective assessment techniques, and the cognitive psychology of subjective workload. A preliminary proposal for a cohesive model of mental load is presented. A bibliographic listing of contemporary research reports completes the volume.