Continuous EEG monitoring can increase the detection of subclinical seizures, and is important in managing nonconvulsive status epilepticus. In the ICU it presents challenges not routinely encountered in the outpatient EEG laboratory or the epilepsy monitoring unit: multiple sources of artifact, and the need for imaging-compatible electrodes and a robust IT support system. Rhythmic and periodic patterns of indeterminate significance are encountered. There is much debate as to the true significance of these patterns, and clinical correlation is always required. Special techniques can be employed in the application and analysis of ICU EEG monitoring. EEG has been useful in monitoring for ischemia, prognosis, and depth of medication-induced suppression. Quantitative EEG can also be utilized to assist in rapid seizure detection, and to monitor for subtle gradual changes in cerebral function and seizure detection. The special environment, however, requires close attention to technical considerations, and thoughtful interpretations of indeterminate patterns.