The purposes of multimodality monitoring mimic the aims of monitoring: to continuously measure relevant biological variables, to verify the effects of treatment, to identify trends in the clinical evolution of disease, and to contribute to the assessment of prognosis. Multimodality monitoring may indicate associations between parameters and may contribute to clinical research. This chapter shows that good data concerning adequate oxygen delivery to the organs and maintenance of homeostasis are already part of routine intensive care unit (ICU) monitoring. Cerebral perfusion pressure (CPP) is calculated as the difference between mean arterial pressure (MAP) and intracranial pressure (ICP), and represents the driving force for cerebral blood flow (CBF). Multimodality monitoring integrates multiple sources of information in a number of possible combinations. It is around for over two decades, and it is tempting to try to undertake cost-benefit analysis of this approach to patient management.