The last decade has seen significant developments in imaging, particularly in relation to the application of magnetic resonance techniques to critically ill patients with central nervous system disease. Most notable has been an increasing trend toward obtaining early spatially resolved information regarding pathophysiology through the use of functional imaging techniques. Although the imaging of critically ill patients in clinically hostile environments such as the magnetic resonance imaging units may represent a logistic problem, the benefits make the exercise worthwhile. Physiologic and metabolic imaging can provide information regarding disease processes at a stage when full reversal is a possibility. In addition, such imaging studies may allow the identification of new therapeutic targets, permit the selection of subgroups of patients who are most likely to benefit from novel therapies aimed at these targets, and contribute to the assessment of efficacy of these interventions.