Several research groups have developed models for estimating the work-related fatigue associated with shiftworkers' duty schedules. In June 2002, invited members of seven of these groups attended the Fatigue and Performance Modeling Workshop in Seattle, WA. At the workshop, each group described the background and conceptual basis of their model, and an independent party compared the models' predictions with performance and sleepiness data from five laboratory- and workplace-based scenarios. One of these models, the Fatigue Audit InterDyne (FAID), can be used to quantify the work-related fatigue associated with any duty schedule using hours of work (i.e., start/end times of work periods) as the sole input. The objectives of the current paper were to: 1) describe the background and conceptual basis of FAID; 2) present FAID-based predictions for four of the scenarios; and 3) discuss the advantages of, and possible improvements to, FAID. The analyses conducted to compare the predictive power of each model are described in detail by Van Dongen elsewhere in this issue.