Adult persons, 17 years old or older, with newly diagnosed (incident) epileptic seizures were prospectively identified in a community-based study. Electroencephalographic (EEG) recordings when awake and/or during sleep were performed in 103 persons (96.3%). Epileptiform activity was recorded during wakefulness in 18 of 101 persons (18%) and during sleep in another 11 persons (10.7%) of whom 10 had no epileptiform activity on wake EEGs. Pathological findings on EEGs recorded during sleep or when awake were more common in persons with partial seizures than in those with primary generalized tonic-clonic seizures. EEG recording during sleep significantly increased the proportion of pathological findings in partial seizures compared with other seizure types. 45 persons (42.1%) were neuroradiologically investigated by both computerized tomography (CT) and magnetic resonance imaging (MRI) using a low-field-strength imager (0.02 tesla). 2 persons with normal CT had pathological findings on MRI. 4 persons with normal MRI had pathological findings on CT.