An accurate measure of mental workload would help improve operational safety and efficacy in many environments that involve multitasking or sustained vigilance. The current study utilized functional near-infrared spectroscopy (fNIRs) to examine the relationship of the hemodynamic response in dorsolateral prefrontal cortex (DLPFC) as it related to mental workload, level of expertise, and task performance. DLPFC responses were monitored with fNIRs while 8 participants (4 with high practice, 4 novices) completed a quasirealistic computerized Warship Commander Task with various levels of difficulty. The results show that greater expertise was associated with relatively lower oxygenation (less neural activity) at low to moderate levels of taskload, but higher oxygenation and better performance at high levels of taskload. For novices, oxygenation was higher at moderate levels of taskload, but dropped precipitously at higher levels of taskload, along with performance, consistent with disengaging from the task. Results are interpreted within a "scaffoldingstorage" framework.