In this paper, we report methodology and preliminary findings focused on the application of multi-level modeling techniques to distinguish effects of sleep loss and task demands on individual and team C4ISR decision making, coordination, and performance over time. We focus our efforts on measurement and modeling. First, we describe aspects of C4ISR scenario development, to ensure (a) psychological fidelity and operational relevance, (b) elicitation and assessment of performance constructs of interest, and (b) equivalence in scenario task demands and difficulty. Sustained operations research is challenged by the need for repeated-measures assessment, while minimizing effects of practice or experience. Second, we describe aspects of cognitive performance based on a standard cognitive test battery. Third, we describe other assessments (e.g. NEO PI personality assessment, mood-state inventory, Stanford Sleepiness Scale, physiological indices) that will be included in an overall approach to modeling fatigue effects, using multi-level hierarchical modeling analyses.