Abstract-Objective: To determine the incidence and risk factors of electrical seizures and other electrical epileptic activity using continuous EEG (cEEG) in patients with acute stroke. Methods: One hundred consecutive patients with acute stroke admitted to our stroke unit underwent cEEG using 10 electrodes. In addition to electrical seizures, repetitive focal sharp waves (RSHWs), repetitive focal spikes (RSPs), and periodic lateralized epileptic discharges (PLEDs) were recorded. Results: In the 100 patients, cEEG was recorded for a mean duration of 17 hours 34 minutes (range 1 hour 12 minutes to 37 hours 10 minutes). Epileptic activity occurred in 17 patients and consisted of RSHWs in seven, RSPs in seven, and PLEDs in three. Electrical seizures occurred in two patients. On univariate Cox regression analysis, predictors for electrical epileptic activity were stroke severity (high score on the National Institutes of Health Stroke Scale) (hazard ratio [HR] 1.12; p ϭ 0.002), cortical involvement (HR 5.71; p ϭ 0.021), and thrombolysis (HR 3.27; p ϭ 0.040). Age, sex, stroke type, use of EEG-modifying medication, and cardiovascular risk factors were not predictors of electrical epileptic activity. On multivariate analysis, stroke severity was the only independent predictor (HR 1.09; p ϭ 0.016). Conclusion: In patients with acute stroke, electrical epileptic activity occurs more frequently than previously suspected. NEUROLOGY 2006;67:99-104 Patients with acute stroke treated in a stroke unit show a relative reduction in mortality.1 Recent guidelines 2-4 have put forward recommendations for the organization of stroke units and defined the usefulness of several acute diagnostic tests, including brain CT and MRI, laboratory examinations, duplex and transcranial ultrasonography, and monitoring of blood pressure, EKG, oxygen saturation, and body temperature. These guidelines also provide strategies for the treatment of acute stroke, including general care and specific therapies, such as recanalization or prevention of complications.However, the role of continuous EEG (cEEG) monitoring in the stroke unit has not been adequately assessed, despite the high incidence of clinical seizures, which ranges from 2 to 33% in the acute phase of stroke, 5 and the potentially harmful effect of seizures on acute ischemic tissue. 6 The information regarding the usefulness of cEEG in acute stroke was obtained in studies on severe stroke patients admitted to intensive care units. Electrical seizures were detected in 9 to 15% of patients, depending on patient selection and the cEEG technique. [7][8][9] In this study, we sought to determine the incidence and risk factors of electrical seizure and epileptic electrical activity in acute stroke patients admitted to our stroke unit.Methods. Subject selection. We prospectively recruited 100 consecutive patients admitted to our stroke unit. Inclusion criteria were acute symptoms and signs consistent with ischemic or hemorrhagic stroke. Exclusion criteria were subarachnoid or posttraumatic hemorr...