<p>High-frequency oscillations (HFOs) are defined as electroencephalographic activity at a frequency above 80 Hz. Activity of this type has drawn attention as a surrogate marker of the epileptogenic zone, and its use as such may help improve seizure outcome after epilepsy surgery. The methods by which HFOs are recorded and interpreted varies significantly among epilepsy centers, however. For recording HFOs, a sampling frequency at or over 2 kHz and an antialiasing filter at or over 600 Hz should be used. The use of intracranial electrodes with a surface contact area of 0.2 to 5 mm<sup>2</sup> is recommended. For appropriate display of HFOs using the viewing software by Nihon Kohden Co., the use of a monitor with at least 1,920 pixels in the horizontal direction is recommended. The high-cut filter should be turned off, a time constant of 0.001 to 0.003 s (corresponding to the low-cut filter at 53 to 160 Hz) should be used, the sensitivity should be set to 1 to 5 μV/mm, and the time scale should be set to 0.5 to 1 s/page. Computerized spectral analysis and automated detection of HFOs are also described.</p>