The high incidence of nonconvulsive status epilepticus (NCSE) and difficulties encountered in rapid diagnosis have only recently become apparent and most neurophysiology textbooks have yet to fully address this topic. There is an immediate need to provide neurologists, neurology residents, and electroneurodiagnostic technologists with information to assist them in achieving early, accurate diagnosis of NCSE in patients they encounter on a daily basis. Instead of attempting to write a comprehensive review of the topic, we examined over 90 NCSE publications since 1972 and focused our efforts on extracting and summarizing those EEG and clinical considerations we found most useful for accurate diagnosis of NCSE in an adult population. The wide overlap between the clinical symptoms of NCSE and many other disorders causing change in mental status limits the usefulness of clinical measures for diagnosis. Those clinical parameters which have some utility are outlined. EEG testing and accurate interpretation is needed to identify NCSE in most instances. EEG patterns of NCSE are detailed and examples provided in order of progressive complexity. Timely treatment reduces patient risk for morbidity attributed to NCSE. Electroneurodiagnostic technologists who learn to recognize the entire spectrum of NCSE EEG patterns are better able to alert electroencephalographers to EEGs likely needing expedited review. This may facilitate early diagnosis if electroencephalographers determine that NCSE is indeed present. Electroencephalographers correlate the EEG pattern, clinical activity, and other diagnostic information to provide the treating medical doctors with an interpretation and recommendation in a timely manner. Lastly, EEG and clinical checklists and an algorithm which uses benzodiazepine response in conjunction with continuous EEG monitoring are provided to help reduce uncertainty in interpretation of equivocal EEG patterns of NCSE.