: Broad sharp waves (BSWs) are a rarely recognized EEG pattern, defined as focal or lateralized high voltage, biphasic, sharply contoured 0.5 to 1/sec waves distinguished from background activities by exceeding their voltage for at least two times. The aim of the study was to determine EEG criteria, frequency, and clinical significance of BSWs. During a 2-year period, we prospectively gathered EEG records exhibiting BSWs in a large EEG laboratory of a university hospital. Clinical variables and the relationship to epileptic seizures were analyzed. Forty-eight (0.6% of 7569) patients exhibited BSWs. In 38 (79%) patients, they were localized over the frontal region. In 31 (65%) patients, no spikes or sharp waves have been recorded. Thirty-four (71%) patients underwent previous neurosurgical interventions. All but one patient suffered one or more epileptic seizures corresponding to a positive predictive value of BSWs for seizures of 98%. A symptomatic etiology of the seizures, i.e., head trauma, brain tumor, aneurysm clipping after subarachnoid hemorrhage, and stroke could be established in all but two patients. In four patients, seizures have been classified as acute symptomatic, in 43 (86%) patients remote symptomatic epilepsy was diagnosed, and in 38 (79%) patients of frontal lobe origin. Broad sharp waves can be considered as an epileptiform EEG pattern on its own. Furthermore, BSWs are an indicator for acute and/or remote cerebral lesions.