Over the past decade, workload has been extensively studied in the field of ergonomics. Most investigations conducted have concerned tasks that require participants to engage in a high level of cognitive processing, such as driving, piloting, and motorcycling. Using a visual display terminal (VDT) to enter data is a common and important task in the workplace. This book reported a series of studies that examined how mental workload and cognitive processes are associated with prolonged engagement on data entry tasks using behavioral measures and electroencephalography. The studies also examined the extent to which mental workload can be modulated by different work/rest schedules. Based on the findings, a mental workload model for low level information processing was proposed and implications for occupational health issues, especially on the design of work/rest schedules for VDT workers, was discussed.