Background: The most important indication for electroencephalograms (EEGs) is the investigation of epileptic and non-epileptic seizures. However, it is unclear whether EEG in the emergency room (ER) can be useful in managing other conditions. Our objective was to investigate the usefulness of EEGs in the ER.Methods: We performed ab observational, descriptive, retrospective study based on clinical records between 2018 and 2019. We evaluated patients admitted to our ER or hospital wards who underwent an EEG. We defined the EEG results as useful when they prompted changes in antiepileptic drug (AED) treatment or clinical management.Results: We gathered information from 236 patients with a mean age of 59.23 (SD±22.6), of whom 47.9% were women. In patients with seizures, 18.2% were generalized, 27.1% were focal, and 18.6% were unknown.Overall, 25.8% of the EEGs were abnormal. However, in patients with a history of predisposing conditions for epileptic seizures or encephalopathies, the tracing was abnormal in 47.5%. The most frequent alteration on the abnormal EEGs was generalized slowing (18.2%).The EEG was useful in 76.7% of patients: AEDs changed in 8.4%, and clinical management changed in 76.2% of patients. The usefulness of EEGs associated with acute ischemic lesions on CT (p=0.023) and with the diagnosis of vasovagal syncope (p=0.022).Conclusions: Routine EEG is useful in the ER, even in patients with a normal CT or MR brain image, as it helps determine clinical management or AED changes.