PURPOSE: To analyze clinical features and EEG changes in patients with sporadic Creutzfeldt-Jakob disease and study the association between different EEG patterns and clinical stages. METHODS: We retrospectively analyzed the clinical features and EEG patterns of 3 patients with clinical stage II and 10 patients with stage III sporadic Creutzfeldt-Jakob disease (EEG n = 17). Chi-square test was used to study the association between EEG features and disease stages. RESULTS: Diffuse slowing of the background was the dominant EEG pattern in stage II disease. All stage III patients showed additional abnormalities, such as frontal intermittent rhythmic delta activity, periodic discharges, and nonperiodic triphasic waves. Periodic discharges had significant association with stage III disease, present in 64 of EEGs in this group. Sixty-seven percentage of periodic discharges had a peculiar pattern labeled by us as posterior-anterior-posterior lag. CONCLUSIONS: The EEG of stage II sporadic Creutzfeldt-Jakob disease is characterized by background slowing while the presence of periodic discharge has a significant association with stage III of the disease. The posterior-anterior-posterior lag of periodic discharge is a new observation.