OBJECTIVE To evaluate the effect of the interval between the seizure and the EEG recording on the yield of early sleep-deprived EEG (SD-EEG) in patients admitted following a presumed first seizure. METHODS We retrospectively reviewed the EEG recordings and medical records of patients admitted to the Neurology Department in Assaf Harofeh Medical Center because of a presumed first seizure during a 3-year period between 2006 and 2009 and who had a SD-EEG following a first routine EEG without epileptiform discharges (EDs). RESULTS The study group included 78 patients aged 18-78 years (mean 35 ± 17). Previous seizures were recognized through repeated history in 32 (41%) patients. EDs were recorded in the SD-EEG in 16 (21%) patients: 13/46 (28%) with a SD-EEG performed within 3 days following the seizure and 3/32 (9%) with a later SD-EEG (P = 0.042) and in 10/32 (31%) patients in whom previous seizures were recognized and 6/46 (13%) with a first seizure (P = 0.05). CONCLUSIONS EDs in the SD-EEG following a first diagnosed seizure occur more commonly when the test is performed within 3 days following a first seizure or when previous seizures are recognized.