This chapter reviews scheduling-related factors that result in sleep loss, associated cognitive performance consequences, and the role of alertness monitoring tools in managing fatigue in operational settings. Three general methods exist for assessing alertness and performance levels during work periods: subjective questionnaires, objective performance assessments, and objective alertness management tools. Real-time alertness monitoring technologies measure aspects of the individual that have been shown to correlate with fluctuating alertness/sleepiness levels. The data are then processed through an algorithm to provide an estimate of the person's current alertness/fatigue level. Biomathematical models of cognitive performance use algorithms that were developed based on the known effects of sleep schedules and circadian physiology on cognitive performance. They provide an estimate of alertness and/or cognitive performance associated with a particular sleep/wake schedule. Facial expression recognition systems are being evaluated as an automated means of monitoring cognitive dysfunction associated with work-related stress and possibly sleep loss.